To me, it sounds like LC is trying to be helpful but has overextended herself. She isn't just being disorganized; she is systematically not keeping her appointments with you when it's inconvenient for her / when the appointments would cut into her own life. She is making commitments to you that she cannot or will not keep.

This is really bad judgement on her part. You are emotionally dependent on her and she's got to know how much it hurts you when her behavior says, "You are not important enough to me to make time for you right now." (Honestly, if I was on a roadtrip with boyfriend and needed to make an hour-long phone call, we would stop and he'd have coffee somewhere.) To that end, I applaud your email! It needed to be said.

It sounds like you have confronted her about this before and she just shrugged it off. To me, that shows that she has no intention of changing her behavior. So that really leaves you with two options:

Accept that she is not a realiable source of support and accept what she does give to you. Or find yourself an additional (or another entirely) source of support.