I would say 95+% of my females will eat right after egg laying if everything is cleaned well; however, there always seems to be one that refuses no matter what I do. When this has happened they always seem to start eating within a week or so after their eggs hatch even though their eggs were taken away and incubated separately.
^This^
So if you have not done so clean the tub well (including water dish), and wipe down your female with chlorhexidine and if this still does not work just be patient she will be ok.