There is no reason at all for you to test for STDs because of this encounter.
It sounds like you don’t normally have things in your anus and putting something in there and moving it around can certainly cause tears of the tissue in there. That’s completely normal, given the circumstances.
The likelihood that the person you were with had some kind of STD on her hands is ridiculously low. I think you should stop stop worrying about this now and go back to your normal life. You are OK!