Look, I don't know your whole story here, but a similar thing happened to me but in my case I was the other friend.
A girl I was friends with in university and I were working on a novel together. It was a lot of fun, but it was more like she was writing it and I was going behind her and cleaning it all up, adding description and details, etc. I did not mind doing that at all. I actually enjoy doing that because it takes a lot less effort to clean up someone else's work than it does to come up with my own, sometimes.
The novel was not why we had our falling out... I'll leave it at that. I doubt you are anything like she was. Honestly, for me, I needed to get out of that friendship, it was toxic.
Back to the important part: She kept the novel. Honestly, it was her story idea. I was just helping. When we stopped being friends, I didn't care that she kept the novel. I was more concerned that she was not going to return the book I lent her. LOL (She did, unharmed)
If Dragoons, is your "baby" then keep working on it.
If you think that your friendship is salvageable, maybe take a break from creating and work on your friendship.
But, if your friend is not your friend because you wanted creative license on your own creation, or you were "spending too much time working on your book and not hanging out with them" then keep working on Dragoons. They are not a true friend if their needs come before your needs. It goes both ways.
One of the big reasons that girl and I are no longer friends is because it was her way or the highway. And any time I disagreed with something, like I did not want to wear matching costumes at Halloween or I wanted to hang out with my boyfriend and not her, then she got mad and I had to apologize.
Also, don't look at Dragoons as a reminder of a failed friendship. Look at it as a reminder of the good times you had. Like a kid caught in a divorce. Don't stop loving the kid because your SO and you are no longer together. Don't let Dragoons suffer 