you can ovulate without menstruation
ovulation is what is necessary for the egg to leave the fallopian tube and travel to where it can be fertilize
it hangs out in the tissues that than become the menstruation after the ova has passed its time in the body
menstruation is the body flushing the old egg and tissues out of the body
it can be bloody or sometimes just a bit of goo...i think the typical amount of blood that typical females loose is too much, probably from toxic diets, environment, excessive estrogen, excessive body fat which promotes hormones (not to say %15 and below is at all ideal for health of every person)
when following a healthy diet and lifestyle, having a bit extra body fat is a way of your body knowing, and imparting to mates, that you are healthy and able to feed yourself and nourish a child properly
i know that all of my time spent concerning myself with weight, diet, fitness, to the point of malnourishment, as well as having been a vegetarian is an enormous part of why i do not ovulate regularly, if at all, and have struggled with it since adolescence...
if your wife is worried about fertility she can have her hormone levels tested...this was how i figured out that my body was producing the bare minimum amount of estrogen(at 25) and honestly the only reason i have had two scant periods in 4 years is because i was packing ON the pounds, i am about 120 now but was probably 20-25 pounds at the time...i know i have had other ovulation a few times but perhaps only 2 or three as my weight is generally around 125(i work to hard and am too poor to really eat the amount of nutrition would like to
..migrant farmer)(i am also not zero carb and wasnt when my periods were restored after 3 years)...i have heard wonderful things about acupuncture as well, and have tried it myself but didnt stick with it due to $$$...i take some supplements like DHEA as well as dr. rons ovaries(mostly i think these help me keep my head on straight)...the lack of estrogen can cause a wide range of health issues besides amenorrhea...bone loss is a huge one, as well as generally expedited generation of the body as females past child bearing age are really not that productive in a more natural sense.....(yeah that is crass but we are put her to reproduce..just like other animals)
if she feels the urge for carbs it is best she listens to her body and figure out what the craving is, if its just too little calories or if her body would really like carbs then it is best to honor that to the extent that is beneficial