[Rivière]

It sounds like your friend has a lot of issues of her own. If she's the sort of person that's dropping friends and making sweeping statements such as those that you've mentioned, where she claims she just forgets they ever existed, then you have to ask yourself, what attracts you to her and makes you feel like she's worth the energy?

You mentioned that you're brutally honest with all your friends, but here you haven't mentioned doing so with her. You've brought up all these very good questions, but if you want to be honest, these are the questions you need to be asking her, as well as telling her how she's made you feel.

Friendship is a two-way thing. If she reaches a point where she isn't interested in putting in energy after a while - for whatever reason - then you need to consider asking yourself why you should do the same.