This sounds like it needs more drying time.
It's very possible that there wasn't enough drying time between the stain and 1st coat of poly. Generally, you need to wait at least 24 hrs before applying the poly with a stain. (Minwax takes longer to dry than duraseal). Sometimes, esp w/ a darker stain and when it's humid, you need to wait 36-48 hrs. Your friend may not have realized this. Then, at least 24 between coats of poly...but if it's humid, you may also need to skip a day. I know this week some of our jobs have been taking longer due to humidity. Your friend may not do this all the time, and may not know when the floors are ready.
I would wait at least another day or two before doing any other coat. If the stain didn't dry properly, it will take longer than usual to dry now that there is a coat of poly. Your friend should screen before the next coat WHEN it is ready.
Also, no one should be walking on the floor until at least 24 hrs AFTER the last coat...and socks only at that point - no shoes, no bare feet. In this case, I might wait 48 hrs after that last coat.
Debbie Gartner, aka The Flooring Girl
http://TheFlooringGirl.comWestchester County, NY