It's not easy to convince! Being 50+ and hearing about blockchain can be mind numbing. It's a confusing thing to get into, but once you understand, you'd have to be crazy not to get involved! :P
I'm sure you can convince her. Just tell her if she writes anything on Facebook or elsewhere, she may as well at least copy and paste it into Steemit, because the value could hit $100 from less than $1 and she can probably afford a nice vacation at some point by simply blogging. Possibly more! :)