I am looking for a noun to suit a specific individual, who "Taught" my previously innocent daughter some very bad behaviors

Solution 1:

With respect, I encourage consideration of a more nuanced appellation. The genteel assignment is “unfortunate influence.” However, simply branding the ill mannered girl will do little to aid and assist your daughter’s happy and peaceful enjoyment of life free of the burden of someone else’s boorish sport degrading her behavior.

Using the term to firmly inform upper level staff and management, or your fellow associated guardians, of the unacceptability of the current arrangements. To describe the offending interloper’s discreditable influence to those in a position of authority and responsibility to rightly require their intervention is the way in which whatever appellation you ultimately find to be appropriate will have a desirable outcome.

Solution 2:

The colloquial term "bad apple" or "rotten apple" comes to mind.