Baby girl name!!! Middle name help!

So my mom passed away nearly 3 years ago and she did not have a middle name and her last name was Rivera and then became her maiden name once she was married. I've heard several places that you can't use a last name as a middle name.. And her first name was mabel and she's Hispanic so her name in Spanish would be Marybelle.. Don't know what to pick.. I loved rivera and I wanted the middle name to have to do w her.. But now it's becoming difficult 😪😪 help!