Sandra refused because she didn't have enough money to lend.
Why do you care?  You didn't need to borrow money.
I resent her for refusing.
Your reaction doesn't make sense to me. If she didn't have any money, you cannot expect her to loan it out. In fact, it's expected of her to refuse.
I guess you're right there. I'm not sure what I was thinking.
It's good that you have come to your senses now.  I believe you don't resent her anymore.