I should start by saying i'm not a Vet, and cannot give you 100% sure diagnosis of the problem. If it were my gecko I would start by immediately mixing calcium with d3 in a dropper/syringe with whatever the animal will take on it's own. Your animal is almost definitely suffering from a severe calcium crash.
I had one female crash hard a year or so back after she laid several clutches of eggs. A pinch of calcium mixed with water, babyfood, peach yogurt, or CGD should be all you need. It may take a week or so before the seizuring stops, and after that she should improve ( if she makes it that long). Remember, your gecko isn't very big, so 1 CC or maybe 2CC should be all you need to give it. Mix so it is still a liquid, with a suspended calcium added it. You don't want a paste, and you don't want to give it too much calcium.
Finally, you need to ask yourself " why did this happen?"
well.... your animal is either not receiving enough calcium, is being over bred, or is not absorbing the calcium it is receiving. There is one very, very simple solution.... Feed only t-rex's Crested Gecko Diet ( CGD) . CGD has everything your gecko needs, and I have never had a crested have a calcium crash since i've been using it. The only thing I would suggest doing would maybe be to add a pinch of calcium with D3 after your female has just laid eggs, after she's laid several clutches. This is by no means necessary, but after experiencing what you are right now, I don't want to risk having it happen again.
let me know if you have anymore questions, but you absolutely must get calcium in your girl today, or she will most likely die ( and still may)
good luck
Andrew Gilpin