Hahaha this is the typical reactions of the elders, it's just not your mom, it's a reaction I have seen many elders do. Initially even my parents were not convinced, but then I showed them growth, and how no one will ever know I own it then they allowed me. Maybe your mom has read some articles that say it's not legal, or your country has not accepted it. You need to convince her that even if it's not legal, no one can know you own it and that it has tremendous potential, best is buy her something out of the profit and don't mind, continue owning Bitcoins.