It sound like you are jumping the gun a bit.
I know its exciting to purchase a new fish, which you then find out is pregnant.
As you said, its not square. Not all females go really square, especially if it is their first batch of fry... If shes not fat, then it could be a recent developing pregnancy, which means, a while to wait yet.
Another poss is, by you movin her, it could of stessed her out, and make her abort.
Its not your fault, just a bit annoying sometimes, it happens to all of us.
If i was you, i would introduce her back into the larger tank. Guppys or any fish, dont like to be cramped let alone be cramped when pregnant.
If you find that she suddenly gets bigger square shaped, and darker around her gravid spot, you can remove her then, or wait for her to have them in the community tank an you wait to fish them out into the fry tank....
thats all i can think of now...
ask more questions if you like, hope that has given you a few options.
