Welcome to Yorkie Talk. There are many members on Yorkie Talk who have larger dogs and Yorkies, and seem to do fine.
I have 4 little ones (around 7 lbs.) and they get along just great with my daughter's 100 lb. Rhodesian Ridgeback.
Of course you have to monitor closely, especially in the beginning to protect the little one, but they can definitely learn to love each other. I don't know anything about Bull Terriers but 30lbs. doesn't sound too large. His interaction with your mom's Maltese is a good indication.
If you are concerned, you might look for a Yorkie that is projected to be a little larger (like 7+ lbs) rather than on the smaller side (4 - lbs).
Good luck. |