You did the right thing- and yes you are a package deal..when I met Danny my kids were grown, but there were 8 grandkids that were young, so I was a package deal too, and he loved the package!!
Your right when it comes to your family. If she doesn't want the whole package then it would be more hurtful to let her and your daughters continue to get closer. My first husband was mentally abusive and we had 3 children. I divorced him and when I remarried my husband understood he had to love us all, and that was a tall order when I had 3 teenagers and he never had children of his own. But he loved my kids and was in heaven when we had our 8 granddaughters, are ninth came just 2 months after he passed away. I'm 47 and if I ever do want to meet someone again they would still have to take the whole package, for me family is everything. You take good care of yours.
My 16 yo insightful daughter said these words of wisdom to me today-------as long as you aren't hurting anyone, don't regret anything that you enjoyed ! All part of this process I think...........peace.
You definitely did the right thing. You can't be with someone just because they're good with your children. You especially can't marry someone to give them a step-mom. The relationship would never work and the kids would be devastated. If you're more relaxed when not dating her, I'd say stop dating her.
Spend the time you would've spent with her with your children. They are your #1 priority and they need you more than they need a step-mother right now. When you meet the right woman .... you'll know. You won't have these kinds of doubts and she won't break up with you every few months. It will work naturally. At this point you're working to make it work .... which means it's not natural and it's not really the kind of love you want for a marriage.
I think you're wiser than you know and your decision to tell her to stop seeing the children is excellent. Stay strong and follow what your head, heart and gut tell you.
You'll know when it's right.