I wouldn't say it's destroyed. She still is high on the list of suspects because you can easily put the "evidence" that should clear her during the party into question by logical reasoning.
Really? Here are the arguments against Delilah from the party that I would like to have explained away (as Delilah would still easily be the top suspect if you could do so):
1. There is virtually no change in behaviour with Ms. X no matter what you do (or don't do) with Delilah. It's easy to see jilted Delilah continuing the act in exactly the same manner as before, not so much if you hooked up with her.
2. Delilah leaving the party when she does makes sense if she is not Ms. X. She either got what she came for (hooking up with Ashe), or when she knows she won't. If she is Ms. X she would have stuck around.
3. How does Delilah as Ms. X know about the Rachel kiss immediately?
4. Why is Fiona lying about what Delilah is doing (says she is sleeping) after they leave the party? I consider Fiona to be the least likely suspect out of everyone, there's no way she's in on it because she didn't know Ashe was a duplo.
Please notice I'm not asking for why messages were received from Ms. X during the confrontation with Delilah. This could have been done with scheduled messages intentionally or accidentally by Delilah.