Regardless of if it's reasonable or not for the parents to pay the hall fees, they said they would! They let her base her budget on the understanding they were happy to pay hall fees - which as catered would leave whatever else she had for herself. They didn't tell her in advance that this offer to pay the hall fees/rent had conditions attached to it, merely waiting until it's basically too late to make other plans, and then withdrawing their offer.
That's really, really shitty. Letting your child commit to a uni course, move away, start the course and at that point change your mind about paying for rent is horrible behaviour.
OP - if your friend hasn't yet, get her to the student union and talk to the uni again, they wno't be able to replace her at this late stage, so it's in their interests to keep her on the course if they can.
She has learned a very sad lesson that the people she should be able to rely on to keep their word, can't be relied upon, and that regardless of what they say, her parents' financial generocity comes with an expecation of having control over her life for that generocity.
If it wasn't uni, then it would be something else, you hear about them all the time on MN - there was one a bit ago about someone who's parents were insistant they would pay for a wedding, but then wanted total control of all aspects from the flowers, to what the bride and groom wore, to the guest list, the food choices etc. (the mother cried and thought the bride was being terribly unreasonable when she threatened to cancel and rearrange a wedding she paid for herself that was entirely to the Bride and Groom's choices).
There's been several threads where parents (and PIL) have given money towards a house deposit, just to think they have a say in how it's decorated, how clean it's kept and that they should be able to come and go as they please, as if it's their own house etc.
Controlling parents often use money as a way to retain control of adult children. Your friend's parents don't give gifts, they buy control.
Dropping out and finding a different course next year after saving might be best for her. And learning to never accept money or help from her parents without expecting it to have massive strings attached (even if they lie that it's just a gift)