Should I keep in contact with my ex's daughter???

My ex and I broke up in 2018 due to him putting his hands on me while I was driving.

It's was an easy decision to make...

But what's been hard is completely cutting off communication with his daughter.I came unto her life when she was 7. I love her! I took her in as if she came from my own womb lol. She even told me she wishes I could adopt her. Her mom did drugs and always ran the streets, so when I came around she clung to me pretty quickly and I wanted to be that role model in her life. She's now 13 and we text every now and then, but I feel as if my ex thinks he still has "a chance" to get back with me.

I am now in a new relationship, and we live together. I'm open and honest with him about everything but he feels like eventually things are going to be messy and I should consider nipping the relationship I have with his daughter before it's too late. I understand where he's coming from but it's so hard.

Any adice???