4 years of stepparenting, she leaves

My fiancé (26f) (J) and I (28f) have been together for four years. We have lived together for a majority of that time but waited almost a year before introducing her to my kids (5 and 7 at the time).

Just a quick backstory. My oldest has no father in the picture and started living with me fulltime a year into our (J&I’s) relationship (I used to coparent both kids with my other ex (34m), my youngest’ father, who was a father figure for my oldest for a long time).

When we met I was not looking for anything serious. But once we had our first date (we met while dancing) I knew she would be the love of my life. She was not my first sapphic relationship. I was hers. We are both bisexual and have known this a long time.

I told her from the start I thought she should leave. My life was hard, very adult, taking care of kids, dealing with their trauma, having little support. It was not something I wished for her. I felt like I was taking her life away and ruining her twenties. I actively tried pushing her away, even while madly in love, which was hard. She asked me to stop, that she would only take on what she wanted and would let me know if it was too much. I had to respect that. A year and a half into our relationship I stopped doing this and accepted she really wanted this. I loved her so much. She loved me and my kids. We both thought we would be forever and that this was it. We got engaged 6 months ago and she met my entire family in Brazil where we went to together.

A month ago she voiced it was too much, too much responsibility, too much to handle, too much parenting, her role had gotten too big (all due to her initiative, even moving in together was her idea). But she was still in love. She still loved me. She wanted to find a way to make it work. We would both think about it for a while. I left to go on holiday with friends for a week, my kids were at grandparents, she had some time alone. When I came back, she said she did not feel in love anymore and thought it as best to end the relationship.

My world shattered. I have never suffered a heartbreak like this. I know I need to let go.

We “coparent“ my oldest together. When I have internships (I am almost graduated as a midwife) she takes care of her a lot. They also have a special bond. She wants to stay involved and keep seeing her. I don’t know how to let this huge wound scab and heal, while seeing her so often (multiple times a day). It’s also hard because I have adopted a lot of her friends as my own that I now don’t speak to anymore, but she (J) has been my best friend for all these years. I feel very lonely, isolated, broken. I have to be a mother while grieving.

How to deal with a heartbreak like this while deciding how her role will look like? So, without going no contact?

And how in earth to tell my kids (now 8 and 10). They have gone through so much already. How do I keep calm and collected while they grieve her?

I am at my wits end.