My cham is the same age as yours but male, i'm also in the UK. I had the same problem a couple of months ago, he didn't go for about 10 days! This is apparently not entirely abnormal. If you can't get her into water just give her a good soaking with warm water from your mist bottle, I did that and sure he enough he went.
Your setup and schedule is virtually the same as mine, although mine only eats that amount every other day. I doubt it's anything serious really, she looks healthy. To give yourself piece of mind might I suggest getting real plants instead of fake ones? real ones look better (IMO) keep humidity ticking along nicely and they're safe for her to chow down on if she wants to.