Using logmein you'd install a client on her computer which would run all the time, then you'd have a web browser open on your computer which would display and allow you to interact with her desktop.
There are "better" ways (as in more efficient, secure, open source and more flexible) but they can be tricky to set up and to get working properly. If you just want something you can download and use straight off logmein is probably your best option there.