Swordtail strange behavior

#1
I just brought two swordtails (male & female) home from the LFS yesterday and after a few hours, they ate dinner quite hardily.

When I went to bed, everything seemed fine.

At about 4am I woke up to go to the bathroom, and on my way back I took a quick look in on the new inhabitants.

The male was fine.  The female was doing barrel rolls, but she was completely verticle -- she was just spinning on her nose, litterally.

Then, before my eyes, she went horizontal and started doing barrel rolls all over the tank, and moving very quickly, at one point hitting a rock and getting stuck under a piece of slate on her side.  :'(  I thought she was a gonner, but because I was really tired and didn't feel like dealing with a dying fish at 4am, I went back to sleep.

When I woke up, she was fine.  She was swimming normally and ate breakfast normally.  It was like nothing had happened.  :D

I went out for the day and when I came back, I mostly expected her to have expired, but when I came home, I was pleasantly surprised to see her swimming around just fine.  She ate dinner normally, and seems fine.

Any idea what happened to her last night?  Is she really fine, or is it just a matter of time for her?