Okay, most people here talking about “is it legal, is it gross, is the ex a cunt, all of the above”.
I’d just like to point out that regardless of all of that, since there is legally nothing you can do, the best you can do is support your daughter. Don’t engage with the toxic ex. Just let your daughter know that you’re not happy about it but that you respect her and support her no matter what. And behave accordingly, don’t get mad at her, show her your kindest side.
What your ex is doing feels like manipulation to distance her from you, in addition to rage bait you. Don’t fall for that.
Flaws in human nature will always be a problem and you will find them no matter what religion and/or political systems any society adopts. It’s as simple as that.