No, don't give her mouthful - do what Shylock suggests.
Write a few notes of the events / circumstances the next couple of times it happens (just to help you explain it) then ask to sit down in a private place with her and calmly and without getting into a heated debate, just explain what you have noted she has done and why you don't think it is reasonable. See what her reaction is. After the event, write your own private notes of the conversation.
If you are not satisfied with her explanation/ commitments, tell her you wish to invoke the grievance procedure. If it is a small company, it probably hasn;t even got one, but it doesn't matter, it should put the wind up here. The grievance proceudre involves you taking your complain the next level of management above - her manager.
Repeat the process with him. You should allowed to explain your side of the story, on your own to him. Obviously expect him to talk to her in private.
At the end of the day the Line Manager above has to help a reconciliation here.