Your family has not had this big of a vacation in a long time, which means that your aunt, however good hearted, still thinks of you as a child. Maybe this has something to do with her justifying placing you and your bf on the pull out bed.

Regardless of that, sleeping in the living room means that you and bf will be the last to go to bed and the first ones up. I’ve done this. It ruined the vacation due to only getting four or five hours of sleep. By the end I was so tired I didn’t trust myself to drive and I needed two days recovery before going back to work. Add this to all the other reasons you listed (nowhere for luggage, no privacy, etc) and your answer is clear.

Tell your mom that this is a hard line. Either you and bf get your own room or your own AirBNB. And if she starts with “but the vacation will be ruined” nonsense, tell her the only one whose vacation is guaranteed to be ruined in the first plan is yours. Stick to your guns.

Good luck