Does your mom know they are much the same? Gerbils just have a longer tail.
All these small rodents are very similar, mice, rats, gerbils, hamsters, voles.
Maybe you should do some homework too, You know gerbils, unlike hamsters, should be kept in pairs or more, they are very social animals. they do need a larger cage and lots of toys, very active and love to play.
Don't get a pet because it is cool, that cool wears off and you see a small fur pet.
I have had all these little rodents, smart, and will bond with you if you treat them right.