Hey, sorry about all that situation.
My advice before collaborating with anyone is this:
1-Don`t jump at every chance of a collab. See if the people with who you are working fits the needs for your project.
2-Make sure you get to know the person. I have some collabs and worked on crossovers here, but before joining any group, i made sure i knew if they were trustworthy before even considering working with them.
3-Check their portfolio. If they have a comic or something like a deviant art account, check it.
4-Don`t let anyone doubt your self worth. If you love writing, go for it, but make sure you have a plan.
Wish you the best!