I think it would be a good idea for me to refuse purchasing my sister a new phone.
What is the purpose of you not buying her a new phone?
She has a lot of clothes already and if she sells some she can get a new phone with that money. If I buy her a new one, she is going to ruin my college fund.
I also don't want to spend money unnecessarily and I also understand why you are having second thoughts of not buying your sister a new phone. But she may really need it for emergency purposes, and her needing to raise money by selling her old clothes may take quite a little bit of time and she may not have the ability to purchase a new phone sooner. How about you buy her a new phone, and have her pay you back when she is able to?
I feel like she needs to learn she needs to figure it out for herself, but I don't want to deal with her whining. I'll probably just buy her a new phone.
It is completely up to you whether you want to get her a new phone or not. While she may need it during emergencies, you also do not want to spoil her I guess. No matter decision you make you will be fine as long as you are doing your best!