Don't bother trying to get this woman to approve of you. She never will. Just be polite, when you are in her presence and try not to react to her provoking you. Your reaction is what she is looking for.

When she gives you a present you can't use, say, "Oh that's lovely." Then drop it off at the Humane Society thrift store. It will buy treats for the orphan puppies and she will have done some good, despite intending to be nasty.

It's not unrealistic to see this lady as a possible impediment to you marrying her son. Now's the time to test how free your bf is of his mom. Maybe she is alienating him, and he will decide not to revolve his life around her. That would be the hoped for outcome. Otherwise, this woman could be a complete pain in the rear for as long as she lives.