Is my guppie ill or about to give birth?

I have 3 guppies in a 7 gallon aquarium, one of them is quite heavily pregnant.

She has been acting oddly for a few days. Lurking at the back of the tank in the plants, chasing any of the other fish that come near her and generally being really narky.

I came into the room earlier and saw that she was lying on the bottom of the tank, she started swimming again when I came closer.

I don't have much experience with pregnant guppies, I've only had these three for a couple of months. One of them has already given birth as I found a couple of fry lurking in the tank last month but I didn't even realise she was pregnant 'till I found them.

I'm pretty certain she'll give birth soon but I am a little worried about her so any advice from more experienced fishkeepers would be amazingly helpful.

Hmm, that's not good.

Anything I can do to help her along?

I've read that not feeding for a couple of days can help if they're a bit bloated.

Right, I'll fast her for a couple of days and leave the light off so she can be as stress-free as possible.

Cheers for your help!