You tell her your dad said NO! Apologize, and hang up. Go back to NC! You are hardly the first guy to have thoughts triggering old feelings of past love made more intense by her text, about "our" cat!
Let this INCIDENT pass without drama, or fanfare, like its supposed to. The last thing you need is old stirred up feelings being stirred to a frenzy by you. Let them go, and they will.
she broke up with me and ran off with someone else
Remember this while you reminisce