I would assume she is "gravid" (pregnant). The fry will be of normal size and should do OK on ground/crushed flake.
When your female guppy is pregnant you can't tell by it's size. You have to look at it's gravid spot. Which is right behind their stomach and the tail. It's right around the butt of the guppy. It takes about a month for the babies to be born. Plus you can not stress out your the pregnant fish.
pregnant
Gravid is the medical term meaning pregnant.
Gravid
Why not? Although the term is gravid, not pregnant.
You will have to go by the size of their tummies. Once a guppy starts breeding she will always have a gravid spot.
There will be a dark spot in front of the fishes anus (cloaca) in a pregnant (gravid) female livebearer. This spot is called the "Gravid Spot".
You have said she has a gravid spot (not gravel). That indicates that she is gravid (pregnant). She would not have that spot is she was not gravid. Be patient. Provided she is in suitable conditions she will have her youngsters eventually.
Many male guppies have 'black spots' but if by "black spot" you mean "gravid spot" then no, a male guppy can not be 'gravid' because gravid is the equivalent of "pregnant" and male guppies can not get pregnant.
Glo fish don't have gravid spots. Gravid spots are actually the many eyes of the unborn babies of certain live bearing fish like guppies, mollies, and platies.
Gravid is the word.
The gravid spot on a guppy is not always a 100% determination of pregnancy as the colours can vary. Quite often, when they are ready to give birth, the gravid spot becomes quite dark.