You've have placed your boundary. Its not up to her to make the choice on whether or not she wants to. The more you do as you just stated - that's just more chasing and begging/pleading.
You can threaten to take her phone away but she isn't your child. If she isn't contributing to the household either directing with a job OR indirectly because she does childcare and keeps the house, THEN have a talk about her need to contribute. But, stop threatening to take her phone away.
Do you really think that taking her phone away will solve OM? It won't. She will find other ways... so stop.
You did good on the conversation about putting the kids first and agreeing on how you would treat each other. Beyond that you went WAY too far.
Real it back in. I know it hurts and stings but stop bringing up her phone and OM.
