ArlenMagic
Also, at points she grooms herself and then grabs my thumb and licks it a lot. Am I going on the right track with this?
D'awww. Sounds exactly like she's grooming you.
smile Sounds like the right track to me. Plus no poop is a great sign! How old is she? I know one of my rats wasn't socialized properly before we got her, and because she was already a full grown adult (almost a year old) when we got her it took her
months to fully adjust. I don't know if it is a common reaction, but the biggest psychological challenge for her seems to be that never being handled made her terrified of heights. Even now, almost a year after being handled daily you can still sometimes see the doubt in her eyes during the very first moment of being picked up. So maybe watch to see if that's the case with your rat, too. And if it looks like it is, then see if you can minimize any heights involved until she fully trusts that you won't drop her.
Just to double-check, if you think she's nervous, then are you giving something for her to hide under while she's socializing with you? For example, if you're sitting/laying then are you putting a blanket over both of you? Or if you're standing, are you wearing something like a hoodie where she can hide in the pocket alongside your hand?