Obviously, it's up to you and I would ultimately send whatever you feel comfortable sending.

I would amend the last paragraph and not make the assumption that it's her giving them short notice... mainly because it reads as accusatory and I would give her the benefit of the doubt until I could speak with her directly.

You may be entirely right that it is her giving them last minute notice but emails can be loaded and/or misread. I would let her know how these last minute cancellations affect you but the rest, I think would be better discussed in person.