Pregnant until moved???

[rsh]

My black molly is in a 29 gallon tank with a male molly, another female, a male and female platy, and an angel fish. She looks very squared off and has a white spot right under her anal fin. I assumed she was pregnant and close to birth, so I put a tank divider on one third of the 29 gallon and put her on the 1/3 side and the rest of the fish on the other. 

She started swimming frantically, so I put towels over the tank to help her not see the other fish on the other side or the barrier and seh calmed down, but she pooped a lot and looks smaller? This has happened twice now with no fry.

I am pretty convinced she is pregnant because of the square belly, and white spot, but am getting very confused by the slimming down without fry. 

What is happening with the fish?

[Guppysnail]

Livebearers have the ability to re-absorb their fry when stressed. I hear this a lot when livebearers are separated from their community.  They choose in times of stress to absorb the fry and retain the resources to produce more fry at a later time when they feel conditions are better for fry survival. They have no parental care instinct but this is an adaptation that allows the most survival of their species. 
There is also a high probability that during stress she is eating the fry as fast as they drop. 
a dense cover of floating plants like hornwort and guppy grass gives livebearer fry the highest survival chance.