Pregnant Platy Top Of Tank

I think I have a pregnant Mickey Mouse platy.  She has been acting a bit out of the ordinary the past day or so.  She swims with the other fish, then hides for a while, then swims again, and then will sit at the top of the tank between the filter and the heater.  Is this normal?  The sitting at the top of the tank is what worries me the most. I'm attaching pictures to show you..they're a bit blurry since they move so fast...any help is appreciated.  Thanks in advance!

Wow she is big! It looks like she will give birth within the next few days. My guppy females tend to go to the top of the tank to give birth and they do like to hide a little. As long as she is eating and her poop looks normal she should be ok. When was the last time you did a water change? Any recent changes in the tank? Temp. decorations, new filter cartridge? 

I did a water change yesterday.  New filter cartridge about a week ago.  Nothing else has changed.  I've seen her poop three times today and it looks normal.  I've noticed that the male mm platy keeps trying to swim near her, sometimes putting his nose (do fish have noses? lol) near her middle and she runs him off and then goes back to where she is hiding, or she'll chase him off, swim out in the open for a minute, then go back to the hiding place.  She's still just sitting there not doing anything.  She didn't come out at feeding time either.

It may be because she is acting sluggish. How long have you had her for? 
EDIT: Also has she ever had fry before? 

If her poop is fine and she seems fine, then most likely, she is probably all right.
 
However, it wouldn't hurt to test your ammonia, nitrite, and nitrate, a possibility would be that by removing the filter cartridge you killed off some of the bacteria in the aquarium which could have lead to an ammonia spike, however, I would be surprised if that would take a week to show up especially because your water change yesterday would have removed a portion of any harmful things in the water. 
 
With that said, your platy is most likely fine, and if you are unsure, it never hurts to do another water change - water changes are your number one instrument for removing potentially harmful things from the tank.