Its a great story thus far!!
Read it today and was really impressed at the versatility of your writing, you have my praise.
As as an avid reader and writer I would suggest closing it with just 4 girls surviving, leaving them completely trusting Diana. In my persoective you should end Val and Kayla in a way that Diana is not involved, like they fight off and fall together a great height and die, something like that, but thats not the point, write what you are comfortable with, its better that way. Just kill off Val, she pissed me off from day one. Keep Natasha and Diana together too, such a sweet couple, kinky and innocent, dont't get Diana to prison when they get bigger neither, would kill the mood. Well that would be enough from me, love your work though, incited me to read your other works.
Have fun and write on, I'm expecting with an open mind the next chapter.