@
offvoice
Yes, I did find out.
In my situation, it was my sister's first ever US trip. So she had to stand in the new ESTA line, and I had to stand there with her. Because they had to get all her fingerprints. When you return with an ESTA, you can just go to the kiosks, where they only check 1 set of your fingers, to match it with your first entry.
If your wife has a new ESTA, but she actually had an ESTA before, she can go to the returning ESTA line. Because her fingerprints are already stored.
Have a safe trip.