I think you need to express your feelings and express the pain old truth.
And this is a new bf right, he didn't buy Bella, so he really has no say...You need to explain from the beginning, all the money and all the care you laid out, and how this is not right and you will not let Bella be stressed or hurt. She is happy with you at your home, she gets to have play time and company with the other dogs at your house, and that's that....everyone is a bonded family at your home - she can not simply take and not take when she pleases
when she grows up, she can get another pet and care for that pet from the beginning (like you did for Bella). Your daughter needs to focus on getting thru college right now and getting a good job after that. The care she would give Bella right now would be half-ass and that's not fair to Bella, her or YOU....