How to cope?

I am really struggling with something right now.  The ex husband is actively and publicly dating his affair partner.  This in an of itself is an ego blow, but manageable.  Now, however, he is very consistently bringing her around my children.  Last week when I was sick with the flu, the four of them went out to dinner at our favorite sushi restaurant (where we are known by name and our kids have their own special dishes).  She spends the night at his place when they are there, though had been sleeping on the couch.  Still not great, but something I was dealing with.  Just moments ago I heard my daughter telling my mom about how the other woman and her daughter spent the night this weekend with them.  After they were done talking, I asked her what their sleeping arrangements were.  She informed me that all five of them shared a bed.  I am so uncomfortable with this.  This woman has already "stolen" my husband and now she is worming her way into my children's lives.  I don't like or respect her.  I don't care for how she parents (this was true before the affair) or how she chooses to live her life.  I believe she is an immoral person.  I feel many of these things about the ex too (increasingly) but he is their dad, so we deal.  I just can't seem to deal with the fact that I can't protect my children from people I think are bad influences.  Any other circumstance and I would have that ability.  But because he decided to end our marriage, I lost this ability.


So I am genuinely asking- how do I cope with this?  How do I find a way to be okay with the fact that this woman who actively participated in the destruction of my family is sharing a bed with my children?  Nothing about this situation is okay with me.  I have no idea how to do this.  I have no desire to share my life with him anymore.  He has shown me, repeatedly, how badly matched we are now.  I am not jealous of her because she has him.  But my ego HATES that she "won" when she never deserved to even be in play.  And now, she not only gets my husband, but my children too???  Where is the justice in this life?  I am truly angry and heartbroken and know that I have no power whatsoever.  It may be the worst feeling I've experienced to date- and I had cancer.