Re: Found a second, un-marked queen under the telescoping cover
It's not too late. Since you have a lot of hive beetles, you need to reduce the space in the hive. If you have a nuc, put as many drawn frames in it as the bees can cover. If the bees cannot cover ALL the comb, the beetles will take the entire hive down in a matter of days. If you don't have a nuc, do the same thing just use the box you have. Remove comb frames until they're crowded.
And, what should be done. Is it too late to save the weak hive? Should I put this queen in the weak, apparent queenless hive, or does she need to be killed?
You need to make dead sure that your strong hive has a queen, however. They might have superseded their queen and you happened to see her. If it does, I agree with Ben. Hang her in the weak hive and go from there. No need at all to kill her.
Try it. What could happen?