yes that one is a female! and she is unhappy most likely due to the lack of UVB.
you need to adjust your lights. Waxies have to have full spectrum unfiltered sunlight, in a wild they spend all day time high up perching under the sun. In captivity full spectrum can be achieved by combining 5.0 UVB and basking spot lamp (UVA) for a tank of your current size, for bigger tanks you can go as high as 10 UVB.
for plants yes air plants will work or pothos too, although my female killed them pretty fast. most importantly you need to cover 3 sides of your enclosure to make them feel safe.
you said her belly is big, but it is not, it is pretty good size in fact for a female

she is good looking as far as proportions go. would you please post pics of the male as well.
water - I'm still confused too as Carlos, do you mean you use filtered water? at any rate don't use it, get a water conditioner ( prime or anything else that is used for fish tanks) and use it for your tap water or you can use bottled spring water.
do not spray them! not frequently anyway, very light misting once in a while and always at night! like once a week is sufficient or once in 2 weeks and do not mist on a frogs. Remember, they need a very low humidity 35-40% max at all the time!