Could the employee have been meaning 150 lbs overweight?
Of course my saying that now sounds like I'm a complete jerk, but it's really just nonsense, if they were saying plain old "over 150 lbs".
For Weight Watchers, their "allowed" weight for a 5'3" woman in her 30s is 140...so if that's NORMAL, 10 pounds more isn't going to cause anyone to buy an extra seat.
We flew not even a year ago, and my DH was totally fine, not even looked at twice, and he was 340 at the time, at 5'10". Not even a problem at all. OK so it was a problem for HIM, and he's doing something about it, but it wasn't an issue with SW.
I did see part of an episode of that Airline show (started in English with Virgin, I think, and now it's here with SW), and a woman was having to buy an extra ticket, but she HAD to have been over what my hubby weighed, and shorter...
OK so back to the question! Check in online 24 hours ahead, be there early, get on and choose your own seats. No biggie. Just don't be late.