Maybe she sees the sign and thinks 3-1 then brings her hands together as she processes that means inside fastball. Taking the sign and interpreting it are 2 different things.Here's why I think it's illegal:
Part of my pitch preliminaries checklist concerning the "appears to take a sign" is saying to myself "fastball, in". Some umpires go with "one-mississippi". Concept is the same, there has to be a gap of time with the hands separated. I don't complete "fastball, in" before this pitcher brings her hands together.
I personally think the best way for a pitcher to take a sign is from on the rubber. Then they don't have to remember to pause.