got a 3 year old female??????????

i just got my female from a co worker and she looks ok health wise, but she is freaking tiny for about 3 years old. she only weighs about 45 grams and there are people selling 5 month olds that weigh much more than her. she has a decently plump tail she doesnt look malnourished but is kinda slender compared to others i have seen of similar size. My question is what can i do to get her to eat she wouldnt eat yesterday and she doesnt look interested in food at all. i never had a gecko that wouldnt eat and its kinda strange to me. secondly is that a decent weight for her i figured she should have been at around 70 grams at least.