Am I being dramatic or was this a bit aggressive

I work online and am self-employed. I average about 20-25 appointments a week.

On average, I'll get 2 or 3 cancellations with 24 hours notice. No problem.
But on average I'll also get 2 no-shows a week. I DO have a strict email I send out for a no show, because, you know, time IS money.

However, I also wait in the online meeting for at least 30 minutes.

I also think you and the therapist should have had a secondary mode of communication for use in case of tech failure. Because it is a reasonably frequent occurrence.

So a therapist/councillor is threatening their clients with debt collection my god ! It is aggressive and unethical maybe pay for your session and cancel your sessions id also leave a review ! Look at better help or something or go through the NHS they offer online services.

Then she really needs to rethink the wording of her standard emails, particularly when dealing with a potentially especially vulnerable client group.

Bloody hell that's really inappropriate even for a new client. Imagine having never spoken to her before, being vulnerable and needing support, and getting that message after having similar tech problems. She sounds a bit too in love with her own importance. Therapy is a profession that attracts some people like that.

I have been self-employed for 20 years in a completely different field and use audio-visual conferencing platforms a lot. That is WAY too aggressive for a reliable, punctual customer who pays on time and never misses a session. Everyone knows that that Teams and Zoom are not 100% reliable and from what you've said, she had no reason to think you'd simply gone waltzing Matilda. What if someone in your family had died, FFS?

I completely get how frustrating it is to have non/late paying flaky customers. But that doesn't apply in your case. In your position, I would feel the trust in the relationship had gone and be unable to continue with her as a therapist.

Shocking- she's known you for 6 months!!!! Could have given you a little leeway! Who hasn't had trouble connecting with teams, zoom etc.
I would complain.

Absolutely don't go back to her. She's ruined any element of trust in the relationship.

She should be charging in advance and then remaining on standby for the entire duration thus never out of pocket. That's by the by, though. I'm sorry you went through this experience.

What are the T&Cs of the session?

Her email sounds like a standard email she sends out if her client doesn't log in within 5 minutes which I assume is laid out in the conditions of booking? Ie "if you are more than 5 minutes late without informing us then your booking will be cancelled at full cost and all further bookings will be cancelled as this service is in high demand"

FFS you paid her for the hour, so she should have been online for the hour (50 minutes, presumably) waiting for you to join, not writing aggressive emails. Teams and Zoom are known for being difficult to connect to, sometimes. I wouldn't continue either, and I would report her to whichever counselling body she is presumably registered with.

I absolutely would not continue, under any circumstances. That's shockingly aggressive and would completely put me off.

I don't think most therapists are worth the paper they wipe their bum with, tbh, but that's by the by.