@awesome9338
Listen, there HAS to be a point where you put your foot down, not just for yourself, but for anyone else who may one day struggle the same way as her. Tell her how you feel, and if she doesn't like it then show her what the consiquences are of wanting to just keep taking but never give.
I'm not saying of ditching her all together. I'm saying tell and show her you're a human with your own issues too, and you only have so much weight your shoulders can handle, and friends don't keep adding loads without at least taking a few.