ps - If what is bothering you is that your wife seems to be winning the closeness sweepstakes by cuddling up with your daughter, you can do well in that contest by being genuinely interested in your daughter's feelings and what's going on for her in her life. Emotional care matters to her a whole lot, at 11. You don't need to snuggle up, you need to be there for her.
It sounds over-the-top to inform Children's Aid. Do you really think your ex is sleeping with your child in order to molest her? That is what you would have to assert to them, and it really doesn't sound like you have a genuine complaint except a feeling that your 11-year-old is "started turning against" you. Girls at 11 can be pretty snippy and sarcastic, and that includes millions of them who are not sleeping in the same bed as their mother. I would just let it go, and deal with the snippiness or sarcasm as issues by themselves. Look at it this way, at least your ex is not sleeping with a series of men, she's just a mommy and her daughter still likes the reassurance of sleeping in mommy's bed. She (the daughter) will grow out of it soon enough.