It depends on the tone, generally (but not always) I find 'good girl' is used by those who speak down to me.
One client who used this a lot was a huge, subtle boundary pusher. Over the years I saw him I made it clear what I would and would not do, he would back off and ask for a second chance. Towards the end he'd stop one thing when I asked him, replacing it with something else to push on. I really started to notice him saying 'Good girl', telling me how lovely I am all the while I'm getting a feeling that he's doing it to butter me up for something, he'd say "I mean it" then go on to a big boundary push again. Each time I left feeling a bit sort of 'groomed'. The last time I saw him I came away feeling worse, so when he phoned asking me for another booking I asked him if he was always going to push for **********. He tried to sidestep around it, I asked him directly and eventually "Yes" he replied, trying to back it up with "If only you I could show you this that will prove you will like it".
Nope, fed up, cannot go on, not interested in feeling like ***** each time.