Hard as it is, ignore it. She is responding so, because she knows he is already regretting his decision. She wants you to react, so his decision is validified. Karma will happen.
My ex (after a year of non contact) opened up that his life had been awful since he left. The 21 yr old barmaid, (soon to be be divorcee) turned out to be a sociopathic, dysfunctional and attention seeking person with serious mental health issues. No comment really, but what was it that attracted her to a 52 yr old, well off executive driving a £40k car, earning more in a year than her husband would in a decade.
I think my ex knew as he was leaving he was making the wrong decision, but (and even he admitted this), he was almost brainwashed. The whole, you don't love her, she doesn't love you, I love you, you love me, etc. He has admitted he was bombarded by texts, phonecalls, manipulation when they met, yet he still went along with it.
You cannot change it, just stay strong. The FB and make up are designed to wind you up. Ignore it. Or go one better. Give her a gift of brand new make up (whatever the cost!!!) To "replace her lost make up". Block her on FB, and him, so you don't have to go through this. Block anyone who winds you up. There are control settings to stop you being abused.
Stay strong Hun, It's hard, but he isn't worth it. Xxx