Pregnant balloon platy

[Thompson2602]

I have a rather large red balloon platy, yesterday I put her in a breeding tank and she has had one fry which unfortunately died, but it's been hours since that happened. I've never bred any fish before however I'm certain this is her first lot, is this normal? Is she already done? Or was that just one that there was no longer space for? She's still huge though so maybe she isn't done yet? Any help any one could offer would be great!