I can relate with your arrival at the "Friend or Foe" mark in life. I had a similar situation occur when a good friend of mine moved into my place, minus the pregnancy on her end. I felt like I was there for her through a lot when she was staying with me, and I have to admit the friendship was reciprocated to an extent, but since I've been pregnant, I rarely hear from her. I have to admit the lack of follow through continues on my end as well though, so I am equally as quilty. Why does that happen?? :)
I think we enter into certain friendships at times because they provide us with a sense of completetion, self assurence, envy, or simply just companionship through times of struggle. One thing I strive and consider a strong standard when investing my time and heart into any realtionship or friendship is integrity. I know its so hard and sometimes leads to the downfall of a friendship, but my advice would be to stay respectfully aloof when you're feeling emotions of resentment for her decisions. If you value her friendship and you are presented the opportunity, tell her how you feel honestly, as a voice of reason- just try to maintain cooth and compassion.
I always tell people I work with, family members, friends, even my boyfriend- If I'm doing something that's causing a tilt in our relationship please tell me. Even if I don't like the confrontation or might possibly try to argue it, I'd rather know than continue performing poorly. Might help :) and you sound like the stronger of you two when it comes to character, she might actually take strong consideration in what you're saying because she probably looks up to you.