Woh! How very self-centred and one-way is this person?!!

No, it does not sound selfish or harsh at all, Canyon, that you've reached the end. What you describe as how she relates to you does not sound like friendship to me, either.

I'm sorry you've had to go through that, where you thought you had someone to turn to in such a crisis time and just got dumped on instead.

With people who make it apparent that they're only able to receive support, I either decide to only interact if and when I'm feeling strong enough to give, distance myself if I find that what they need I ain't got, or in the case of it being a family member I try to remember to keep my expectations realistic so I'm not let down.

If it's a case of her just using you (and I do like your analogy there), I think it would be quite healthy of you to move away from that - like letting her know you're not available when she contacts you for a ride again (cos why get taken for a ride again?!)