It's a shame the photo isn't a bit sharper. By the early '50s, that style of .22 rifle had been made by most of the "big" manufacturers and a number of others that had already faded into obscurity. It might be possible to narrow down the possibilities a bit, but nailing this down with full certainty is doubtful.
Dean should try to determine whether Bella has any surviving family. Regardless of the make and model, the rifle could be in someone's closet today.
What a find that would be!