I love my grandma more but don't want to upset my soon to be stepmother?

Ok so my Dad and my Granny (his mom) raised me from birth alone. So my Granny (and I) likes to think of herself as my Mother. Well my Dad has been engaged for a year now and I'm semi close with his fiance. The thing is I always get my Granny something for Mother's day because she's the only one I've ever had. But this year I'm going to get something for the Fiance too. I'm going to get my Granny something that she wants but I don't know what to get my soon-to-be stepmom. I don't want to get her as much as my Granny but I don't want it to be obvious and make her feel bad. Anyone who knew the situation would understand me wanting to get my Granny something better but I don't the soon-to-be would. I think it would hurt her feelings even though she hasn't been there for me or done the things that my Granny has.