By all means tell the receptionist and anyone/everyone you can.
But don't let STBX know she is even on your radar. Zip. Zilch. Nada. She doesn't matter. He doesn't matter. I know it sounds counter intuitive but saying anything makes them feel powerful, even if you're insulting them.
Trust me on this, OK.
NC IS hard in the beginning. At first we want to break it to beg them to wake the fuck up and then we want to break it to unleash hell on them. Both are toxic to you.
It won't always be this hard. One day you actually won't give a flying fuck what those parasites are up to.
She didn't get your life but she'll get the one you were going to have - the one with the lying, cheating scumbag.
An article that helped me pity his whores is the second one down in this link, "Because You're So Special".
You can't shame them because they are shameless and completely devoid of empathy or integrity.
Stay strong and hold fast to NC. I promise it won't always be this hard.