I agree that the attitude of Claudia's parents sounds irrational. Irrationalities like that usually indicate one of two things:
Miscommunication: Claudia and her parents aren't getting their messages across to each other.
Uncommunicated reasons: Claudia's parents really don't like her dorm, or don't think the space is adequate for two, or think you'll stop living with her if she has an apartment. Or something. Finding out these real (or additional) reasons is a first step in negotiating a settlement.