Oh dear, I was quite shocked to read the first replies to this question, I mean... maybe because I'm a latina, but in out culture, parents have a child to give them EVERYTHING, my parents always have helped me out if and when they can.
People should stop judging NiceCupOfTea, we don't know what kind of debts she has, one thing is if she is a crazy irresponsible one that goes around shopping and not thinking in the consequences, other VERY different thing is when you want to study, to be somebody better in this world we have, and you can't just because of lack of money whereas there are so many rich ones who are superficial and don't even think about studying.
I think if your dad has the money and it won't make a damage in his life to give it to you, there is no harm done. Yous sister is just being jealous, if she also needs money, she should go and talk to him directly, it's ridiculous of her to say she is proud of asking him.
Good luck for you both, and careful with the loans, hehe! ;o)