Oh boy... my response is going to be risky as it appears to go against the grain of the common thread of responses here:
M., I would, like you, feel angry, frustrated, and concerned about the style of care this young gal is bringing and I, too, would act accordingly to find a different care provider for my precious young ones when faced with concerns for their safety.
However, the young teen here is exactly that.... young (whether emotional, or otherwise). It sounds like she's getting a bashing here on mamasource; how would she feel if she read these very negative responses about her? A future mother, herself?
Although I have the privilege to communicate, find comfort and support at this venue and that I appreciate that we mom's MUST protect our childrens' innocence, I am compelled, at large, to understand why this sitter isn't cutting it as a mama's helper (for her very own reasons/issues). We ALL have issues AND we ALL need support to grow through them and find resolve.
Geez, by taking a prevalent tone of harshness we really may miss the opportunities to assist anybody. Educate, empower, and inspire with a tone of love and understanding (with good boundaries) and see the potential positive results!