Get a smaller enclosure temporarily something like this (Sterilite 2.7 Quarts) http://www.walmart.com/search/?query=sterilite%202.7
and aim for 80/82 and 90/92
I used to keep my hatchlings until they reach 20 grams in those (now I actually use even smaller tubs since I have a Pencil Box Rack)
Try feeding live pinks.
Do you know how many meals were fed before they sold this animals to you? Do you know if it was scented or unscented? How many F/T
Do you know for sure if it is a female (male are more prone to go off feed)
If you do all that and it still does not work here are some things you can do (it is a step backward but sometimes you got to do what you have to do in order to get them on the right track)
Scent the pinkie with either
Tuna
Chicken Broth
Salmon
Anchovies
Toad
Might take different tries with different scents.