I wouldn't bother with a gerbil honestly. If you've got a live feeder it's dangerous to put a live gerbil
in the enclosure for feeding. They are notoriously more aggressive, have much sharper teeth, and sharper claws. I'd keep with what she was eating.
A couple questions.
What's your set up like? Tank? Temps? How are you heating? Things like that with AS much detail as possible

Do you know this is an actual female? Males are notorious for breeding fasts. But girls are not exempt. Sometimes they hit the 1000g wall. Which it sounds like yours may be at. It's normal, but something that I've found is to feed weekly smaller meals, and keep them in a smaller enclosure. I keep girls in 15-28qt tubs depending on size. I don't move girls out of the 15 qts until they're a good 1500g. There abouts. It also depends on the female. So you could try a smaller enclosure.

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