Hey there. I'm 19 and my parents were very kind in offering to buy my plane ticket if I wanted to go to HI and visit my grandma. She only recently moved there, and I have never been. I have no real desire to go for the Hawaii part, but I love my grandma. She lives in a 750ish sq ft studio apartment by herself.
 
My school break that I hope to go is also a week before my boyfriend and my 5th anniversary. I asked if he could come (NOT on their dime, him paying) and my parents said that would be fine. I expressed that I wanted to find somewhere to stay with him(him and myself paying, I made this clear), and they said that they would not be interested in paying for my ticket anymore. 

The reasoning is that if they pay for my plane, I should save my money. My brother is with my Grandma right now and he is staying in her apartment. I understand that they want to help me, but I don't quite see the connection. 

Thanks a bunch for reading

TL;DR: My parents offered to buy a plane ticket, will not follow through if I choose not to sleep on the floor of my grandma's studio apartment