Calling irc ‘useless’ is a bit much. It’s not as popular as it once was but I’ve come into contact with (and keep in contact) with some very informed people courtesy of irc.
People need to experience something before they can ascertain if it is a viable option. Install Ubuntu or Linux Mint on a secondary device, let her see how familiar it is to her.
Then you can explain some of the other advantages of using Linux.
Because Threema is better.