HCA: Hermit Crab Association

I recently got a new crab, she is tiny and pale with a very purple pincher. I put her in an iso tank and have been taking care of her like I do for my others while also supplying her with carrots. When would you say she’s be ready to move in with my crabs? Both of them are large.

How long have you had her? If you have monitored her and she is free of mites or signs of shell rot, then sure, why not! HCA Care sheet suggests a feew weeks up to a month of this

I have had her for a few days, probably about 3. She is in her iso tank but I cannot find her, assuming she’s molting.

Many of us just look the new crab over to ensure they look okay and don't have any mites, then put them right in the main tank. Giving everyone a quick dip in the fresh water will ensure everyone smells the same, and nobody smells like a 'newbie'.
If you have an iso tank and your crab is already buried, don't dig them up. Be sure that the temp and humidity are both optimal, and wait for them to come back up.

Her legs are very pale with a little bit of gray on her legs. Based on photos I have looked at, it is not shell rot or mites and she did come out from hiding.

She is completely buried somewhere in her iso tank again. Her tank is humid and warm. She has plenty of food and water. She has saltwater as well.

She may be de-stressing, as I got her recently.