I'd go through and weigh the rest of the feeders, at her weight a 15% meal is 18 g and a 20% meal would be right at 24 g. If you weigh the rest there may be a few smaller ones in there.

She may be able to take a 24, but I'd try to start with the smallest feeder you have.

I usually weigh my new feeders when I get them and split them up in ziploc baggies based on weight that way I can work my way from the smallest stuff in the order to the largest ones. For fuzzies and pups I'll do like a 3-4 gram range on the baggies, depending on how many of what size there are, and once I get up to smalls and mediums I'll go with generic 10 gram categories. It makes meal prep a breeze for my quickly growing collection.