Sounds to me like your daughter's "frienemy" is a covert narcissist / psychopath using a common form of mind control to break down her self esteem, will power and sense of identity, in order to have her not have any sense if identity outside of their "friendship". I hope you nip this in the bud because that form of abuse can cause a lifetime of issues of inadequacy.
I would suggest you show your daughter the "mean/nice cycle" and "gas lighting", as these are common techniques used by psychopaths just to let her know that these are real things. I really hope the best for you and your daughter. Good kind people with good hearts are always the target for these people.
psychopath seems quite a bit of a stretch. lol