I don’t see it as definitive proof that she lied. It might have been both things i.e. she did indeed book an appointment at 12.30 seeing she had to let you go early.

If it bothered you, rather than asking (and accusing) her with a ‘why did you lie' I would give her the benefit of the doubt and ask her to clarify my doubts (‘did you let me go because of what you said last week or because you had a client’?)

Sadly, the monopoly for lying does not rest with therapists. It seems to be a ‘quality’ favoured by the human species. However, it is always better to seek clarification first rather than go all guns blazing.

That being said, shame if she *did* lie - there is no excuse for that.