That sucks- I am sorry you went through that
No provider should ever NCNS unless it is a true emergency, and in that case she should contact you asap to apologize and/or offer to rebook or make it up to you. That is purely unprofessional.
As a provider who took a hiatus and am recently getting back into providing on a limited basis, I'd say to shoot her an email or text asking what happened, there may be a legit reason and give her a chance to explain and make it right. However, it seems more likely than not that it was some sort of mis-communication or double booking situation.. Either way, NOT at all professional and rude to you.
That said, I would highly advise you, to ensure the best quality of service and consistency, to make sure you have read the profile and all the reviews of the provider you are considering meeting, and preferably book your date in advance. It seems with 2 hours notice and a last minute switch to a roommate of the initial provider, I am guessing the TER check may not have been done (forgive my assumption if I am incorrect)?
Most reputable providers will have good reviews, will screen well (there is no way in my thought process, if this was a second hand arrangement, and on such short notice, that she could have done so-- thus my other though is that she got nervous/paranoid about it due to the circumstance) but perhaps her roommate did the screening and thought she'd feel comfortable since it had been done??
I don't know the specifics, more details might help us better understand what could have happened, but it's of course hard to make assumptions.. That said, I do highly recommend seeing providers with consistent TER reviews and profile, good screening and booking (for example, my ideal is to book a week out when possible, due to the time needed for thorough screening and my busy schedule w/ school and other commitments- not implying that a provider who can take short notice bookings is any less professional, just that if you think about it, screening and such show she protects her own safety and participation- if she does not look out for herself, how can you trust her with your info etc. and trust her to respect your equal need for privacy and safety? Does that make sense?)
Hope some of this helped, and again, maybe I am grasping for straws here since I don't know the whole situation, I know it can be easy when you are anticipating an appointment and relaxation and are presented with the option of another provider or sub, and you find her attractive, to accept that, but that might not always be best if you don't have time to establish that she is reliable and safe and establish good communication.
I am again so sorry you experienced this, this should never happen and is not acceptable no matter what, and I wish you better luck next time!!
xoxo