Not sure. I have the same issue with my Gold panda molly. She wasn't this puffy when we got her about a month ago, so Im not sure what's goin on with mine either What I did was, look up my molly's pregnancy info. How long should they be along before they give birth, watch for any eating habits that change, behavior in the water etc. Also look up "pregnancy behavior" for your fish. Some fish do similar things, some have lil quirks about them during pregnancy (Or, if they have bloat/dropsy etc). Mine has white stringy poo, so could be constipation/parasite issues with mine. Not ruling anything out yet. Once you gather info on your specific fish species, step back and take a look at every box you're able to check off. Maybe try some methods that treat dropsy/bloat (that wouldn't compromise a preggo fish), and see if anything changes. If it changes, it might be one of those two. If nothing changes, wait a week or two (or however long pregnancy cycle is) and see if she gives birth. If time passes, I'd try the medications again?
Im fairly new to this aquarium hobby thing, and I still have a lot to learn, so take my info as suggestions, not "pro". Hope you're able to figure it out! Im still waiting to see what happens with mine. Bought ours on Dec 28th.