it's a combination of what's been said above.
that said... as always seek legal advice....
from what I can make out.
you have a client, (woman A) who has asked you to make a website.
you've made the website, but haven't put content on it (as you're a coder not a writer?)
you've given some SEO advice, (I guess that is stuff like, name articles well, update often, with quality updates, etc.)
At this point you have provided a website, that is just awaiting content.
Woman A the business owner is not a writer either, so she has asked Woman B to write content.
Woman B has a badly made website that is not responsive, but still has asked to see samples of your work, to decide if she can work with you?
And has said that if she finds that she cannot work with you, she'll take over the site. and replace your advert at the bottom with her own.
or woman B may decide that she can't work with you and will take over the site, contract out development to another 3rd party to actually add the content that she writes, and they will replace your advert with their own,
(though in both cases they will presumably still use the actual site template that you made?)
so...
(this is where a good contract would have saved you.)
Woman A, provided that she pays you, now owns "a copy of" the work. she has rights to add content to the site. though (unless your contract with her allows it.) she cannot resell the template, formatting, layout etc...
Woman A, is free to employ Woman B to write her content.
Woman B is fine to write on every article that she writes that the content is provided by her, (though I can't see that woman A, who wants to run a business is going to look too good with a website that has loads of adverts on the bottom! she will likely want the articles "ghost written" meaning that they come without attribution!)
if you have a site where the articles that woman B writes are not going into a content management database, but actually to plain files that the writer has to update, then either Woman B will need to update the code, or employ some other agency to update the code each time an article is published.
3rd party design agency C cannot put an advert for their company on the bottom claiming that they have made the site that is your work. (because you would most likely retain copyright on your artistic en devour. - but check your local laws.)
Really, I think that you have five courses of action.
1, find a better content writer and show your client how the one she chose is bad, and that she should really use the person that you've found.
2, work with the writer, (Woman B).
send her a simple email like this, additionally copy in your client, so that they can see the kind of person that they are employing.
Hi,
Thanks for your message asking for samples of my work.
I'm confused by your message that you are not sure that you will be able to work with me, and may employ a 3rd party to update the site with your content, and that they are likely to replace the link back to my site with their own, I would suggest that if you find that you cannot work with me, you should advise your chosen partner not to claim attribution to my design work, or derivatives of my design work, as these are protected by copyright law.
that said, I have investigated your work, and hope that we can work together on this, (and possibly other) projects.
you can find links to my work from my portfolio on my website here: (add a link to a portfolio section of your own website.)
3, say nothing, and wait for the writer to steal your business.
send samples of your work, but say nothing else.
wait for the writer to send the work to the other design agency, when they claim copyright to your work sue them.
simple and effective.
you could even leave it a little while and try to figure out if the other design agency not only fraudulently claim to have designed the designs that you did, but also if they outright steal them and re-use them elsewhere. - that builds a better case!
4, send the designer samples, and prepare to walk away. but send your client (woman A) a message to the effect of this.
Hello,
Just a quick note, i've had a message from your content writer asking me for examples of my work saying that she "may not be able" to work with me, and "may" need to bring in another designer that she can work with.
I've been in this position before, from my experience:
My other work has no bearing on your site, so it is really rather strange that she would need these examples.
It is quite unusual to start a professional conversation from the position that you probably cannot work with other professionals.
This sort of conversation only happens when the new party, has a second business, or friends/family that they want to bring in.
the conversation usually goes something like, I can't understand what the writer means, or some other small thing that is grown out of proportion and leads to a toxic atmosphere.
Whilst I will try to work with the content writer and have, as requested, sent through samples of my work, my experience tells me that I may be replaced soon, and therefore would like to take this opportunity to say that I have enjoyed working with you and your business whilst designing your website, and hope that should you require more design work in the future that you would consider using me again to update your website when that is required.
The content writer has also suggested that she will remove the small advert that I have placed on your site linking back to my site saying that I designed and created this site with a link of her chosen partner claiming that they designed and created the site. should it come to a situation where I am no longer working on your website, but my designs are still used, can you please take steps to ensure that the attribution for the design remains with me, and is not replaced.
5, say nothing, do nothing and just walk away.
the writer sounds like an idiot, the 3rd party design agency that she's saying that she wants to bring in sounds like her boyfriend or family or something.
she sounds determined that she wants all the business coming from that agency. so let her take it. walk away, when they claim copyright for your works. just ignore it, link backs are overrated anyway!
it may be in your interests to send an invoice for the work so far ans walk away. - of course, you will want to wait until you are canned before walking away.
But if you were waiting until the end of the contract to get paid, it may be a good time to ask for some money for the work done so far!