At her weight are you sure she's not eating? Do you count the crickets when you put them in the tank? A feeding bowl would be a very good idea at this point I think, crickets are notorious for getting back behind the false backgrounds and dying off :/
Just make sure you don't block off too many vents as RETFs need very good ventilation. TOO much humidity can be as bad as too low. I think I'd go slow and check a few different things as you go along. Try just misting with the vents all unblocked first, if that keeps her between 60-70% then great, if not then move on to the next thing to try... too many changes will be stressful on your frog too.
Probably would hold off on the fogger for now until you see how well the humidity does with just misting a few times during the day. Humidity naturally goes up at night, so I probably would leave it off in the evenings if you do use it.
I'm hoping a RETF expert will chime in here as I am not an expert on them by any means; I don't own any, so am giving advice based on research...! :P