Midwife isn't very nice!

Jessica
Me and my midwife do not seem to have a very good relationship. She is quite an odd, mardy older lady and it feels like she likes to catch people out and gets a thrill by doing it. 
Stupidly at my first appointment I told her I used to smoke cannabis and I occasionally had a cigarette (before finding out I was pregnant). 
She there and then made me blow into a breathalyser to test my carbon levels- come back the same as a non smoker. 
She then advised she would be drug testing me and if it came back positive I would need to see the drug counciler. 
( she never mentioned anything after that).
Fast forward to my 28 week Midwfie Appointment and she wants to drug test me again (which is very clearly to try and catch me out). I accept as I haven't touched anything in that nature and never would put my unborn child at risk. 
Both tests I have now passed, so if she is to ask me again or tell me she's doing a drugs test I will refuse it. This is okay right? More than once  it's been proven nothing is in my system. 
Also she will be having a little go tomorrow (33/34 week appt) that I haven't booked any antenatal classes as my partner has children. Any questions I have can be answered by him or my family. 
Hopefully I will only see her once/twice more then never again!
She won't be getting a thank you card or chocolates from me 🖕🙋🏻