Overly sensitive rat??

I recently adopted 2 new girls into my mischief. Their names are Whimsy and Waverly. They are both super sweet and very active (under a year old) and have so far gotten along great with my other girls.

I am having an issue with Waverly though. Some background that I got from her previous owner is that Waverly is a former lab rat, used in memory studies. I have no idea how long ago that was or how long she was a lab rat, but she is shy and jumpy at times, but overly curious and cuddly with me and my other girls for a majority of the time. The issue is that she screams. A lot. At the slightest things. She will sometimes freak out when my other girls try to groom her, or cuddle with her, and she will sometimes scream when I try to pick her up. This isn't a constant thing, it happens randomly. There are times she is totally into the grooming and play, and she will let me pick her up just fine most of the time. But when she gets like this, I genuinely think my rats are tearing each other apart and I freak out, but I've sat and watched for hours to make absolutely sure there was no actual fighting, and there isn't. There are just times one of my girls will go up to Waverly and start to groom her and she will start screeching and jumping like a flea.

I currently have her sitting with me in her carrier cage to let her have some space, but I'm just really lost. Is this something I have to let her get over? I did my usual introduction process for a week when I first got the girls to let them all get used to each other and things went great until I moved everyone together full time. She doesn't seem to be distressed when these fits happen, and she'll run right up to me when I check on her, but I'm worried. I don't know what to do or if there's anything I can do. I don't want her or my other girls to become distressed. I haven't asked the previous owner yet if this was an issue when she had the girls, so I'm not sure if this is just how she is or not.

Any and all advice is appreciated, thank you