When you're laying face down for a massage, you can close your eyes and block out everything, but it's impossible to block out any smell, and that for me makes the whole experience so bad. The other thing I always check is the sides of the hole when you lie face down. Even if they place a towel on top, I always end up pulling it down to cover the sides where others have squashed their face against.
I would leave an honest opinion if there's no plan to return, it's not like its all negative.
But if she's good, is it worth asking if she does home visits so you can control the environment?