By the way, I have realised I didn't answer the OP's question. Here goes:
No, you are not being at all unreasonable in feeling a sense of resentment towards your friend. What this 'resentment' is telling you is that your boundaries have been transgressed and that things are 'wrong' in your relationship. You need to listen to this feeling; to acknowledge it, to accept it, to act on it.
Friends are people we have invited closer into our lives. We extend trust towards them, usually based on previous experience in which they have shown themselves to be worthy of trust. We lower our defences with friends because we expect them - by and large - to act in a trustworthy way with us: we expect their actions to be modified by some acknowledgement of our well-being, by a knowledge of us - our wishes, likes, dislikes, and - yes - our long-term interests.
We probably don't expect out and out self-destructive altruism from our friends. It's nice if we get that (though a little onerous) but we can, reasonably, expect a friend not to trample all over our self-interests in favour of their own.
Generally, when people act in this last way, we cease to consider them 'friends'.
Your 'friend' is manipulating both your gender-socialised bias to be 'nice' and your 'friend'-relationship in order to exploit you. You are giving money to her that you can't really afford. She is now exploiting your friendship-networks, and turning you into someone who is exploiting your other friends for her benefit - not yours.
Of course you are feeling resentful.
The question is, why are your boundaries so poor that you are allowing this to be done to you? And what are you going to do about it?
It's important to answer these questions because, as people, we experience new situations and we change and grow from what we learn in those situations. This is an opportunity for you to learn a little about yourself and become more resilient and self-loving. These are good traits - and they will make you a better friend and more of a friend to yourself. 