I always thought Ryan killed the girl and Titus tried to help cover it up. Perhaps I was wrong.
that was the common belief, that Ryan injured her badly and the 3 of them buffooned their way thru trying to fake an OD, tazing to cause heart failure, then of course, strangling her when all else failed. The idea being to make it look like they discovered her after a bad accident. Story goes, she ran up credit cards and other debt using Kelly's name and well, Kelly caught her and she played broke.
Once they realized their fingerprints were all over a homicide victim, the only option was to hope a fire would destory all evidence of it, and just look like drug OD in burning car. Things didn't burn as planned, and the walmart video of Kelly buying fire chemicals was the coup de grace to their defense.
They're walking with a gift of a plea, and Craiggers did do the honorable thing and fall on the grenade for Kelly. Face it, he's built for prison, and she's not. He'll be fine in there - you can see he's lifting in there and will be popular thanks to his experience and knowledge. She'll do her 2 to 5 and come out and quietly fade into a retail job somewhere.