For a remote nontechnical user, coaching them through installing a Tailscale client that registers to your account seems pretty accessible.

If you can get on a screen share with her through something like Signal desktop, then walking her through the steps and pasting a WG key in chat might not be so bad.

I suggest using a client that is easy for her to update without requiring a call. Another point for Tailscale I think.

It does in the version I am using