Majority of people have to learn it through their own personal experience, so they tend to not care much about safety until they get screwed. You did what you could, explained her all the risks and now its up to her. Dunno, maybe get her hw wallet as a present, maybe then he gets bothered to check it out, and hopefully use it.

It it at least one of those more "secure" exchanges like Coinbase/Binance, or she is keeping her money in one of those dodgy ones like HitBTC or P2PB2B?