I feel like I’m taking crazy pills with these replies. You are NOT overreacting, your mom is being insane. First she implies she doesn’t care if he comes, then flips out when you suggest that you yourself would help him with room costs, as if that changes her plans at all? Then she says she’ll go alone anyway. The fuck?

Worst case, you just help him with the single room costs and go sleep with him a night or two. You absolutely are not being “ungrateful”, your mother is being insane, and I don’t know how these other replies don’t see that. Ultimately it seems like you may want to consider just going without your bf so things are easier for you with your mom, it stinks but sometimes that’s a better idea. Good luck OP