It's hard to see with the red light, but if she's not trying to pick at it and the others are leaving it alone, then I would just leave it alone too.
I might heal up on it's own just fine, especially if she's eating/drinking and able to poop o.k.
Welcome To BYC
Can you post some photos?
Generally, if the navel is closed but a little string is attached, just leave it alone but let's have a look to see what you see.