I'll own up to it. I also was wondering why she was "fidgeting" at first, because the context for her getting horny didn't make sense.
It's not like we haven't seen Roxy just openly pleasure herself before...
Then I thought about it and realized she was having a fear moment, but also wondered if this series was really about to go that graphic while in that composition of shot.
It also makes it strange that she has no issue going at herself in the hallway of her client's house, but reacts prudishly towards Whore Elf having orgies in their inn room when Roxy is away for the day.