I have a friend that is really invested into crypto. She is very enthusiastic about it and I learned a ton about Bitcoin and crypto from her. But then she told me something that scared me: she keeps ALL her Bitcoin in the exchanges rather than a hard wallet.
I think it depends on how she is using that investment. Knowing that investing in something like Bitcoin would be ideal and trading it in the exchange easily with fees low unless she is going to withdraw it or something. Swapping in a hardware wallet is costly if you want to really profit in trading so, it depends on what the application of her with the investment.
I told her that was a security risk, she could get hacked, the exchange might play dirty with her money in the future, the exchange could disappear. Her response was that I was being paranoid, that her exchanges are safe, and that she is pretty careful anyway so she is certain hackers won't get her.
Maybe you can convince a portion of her investment portfolio to be kept in a hardware wallet instead of staying in the exchange?