When dealing with Scientology execs, the only way to hold your ground is to be prepared to be as nasty as you need to be, and to have a reputation for becoming "unpleasant" when somebody gives you shit.
Never be polite. Never be shy about defending your space. They will roll over you if they sense weakness. I'm really serious about this.
From this point on, I suggest she prepares a "nuclear button": make a video recording on boyfriend's phone, wherein she declares on video :
My name is XXX. I am afraid that at some point the Scientology organization may attempt to hold me against my will, in order to use undue influence to subvert my will. I authorize my boyfriend, XXX, to call the police on my behalf if I do not leave the Scientology building when he expects me to.
If she is prevailed upon to go in for "handling" on "routing out", and she is not out on schedule, and has not called boyfriend to say "I'll just be a few minutes more", boyfriend can walk into reception, and tell them "Either she's out here in 5 minutes, or the police will be called". (Keep a backup copy of video on laptop or with a trusted friend.
Best, approach, though is to not let it get that bad. Just say bye. Don't go back.
I'm saying the above for the benefit of boyfriend, who may not believe how ugly it might get. Yes, it CAN get that ugly.