In my opinion, you should get some new chicks asap. She'll have time to wind down while they get older, and after a month or so you can move their box to her coop-so they can see but not touch each other. Every once in a while you could maybe hold the pullets near her or let them walk, so she gets to interact, but not letting her touch them. Eventually you can take the box out. For a few days there will be pecking, to determine their places on the pecking order, but there shouldn't be serious injuries. (If there are though, remove the chicken immediately!)
We did this to introduce four into my flock of three. The younger gals are at the bottom of the pecking order,but they all get along well enough.
Your hen will get lonely and sad if she's alone; chickens are social creatures. You should always try to have three at a time.