*Edit*
the spot that caused the injury
Like I said I didn't really watch much of the match and I never saw this. It does look this was it and not the moonsault. The moonsault could have been a catalyst tho but the twisting here does look pretty nasty to have been it alone.
Edit: The Tweet below also could have been a factor. I have no idea where this took place in the match, during the commercial or live broadcast. The fact is she took a lot to that knee that night.
Edit 2: I watched the Live Broadcast. Charlotte does the moonsault, there seems to be no visible favoring or limping so I was wrong there, then they cut to commercial. They come back from commercial and they go right into the corner flatliner spot were Charlotte twists her knee. So this tweet below must have happened during the break. I do not think she hurt it there because again she was not limping going into the corner when setting up for the flatliner spot. I believe 100% the corner spot where she twisted her knee is where the injury occurs like the gif posted indicates.
Now whether those other spots, the moonsault and hitting the ropes, compromised her knee is something we will likely never know.