Lately my wife is feeling the need for so much sweets what might her body is signaling for?

Cravings. Unfortunately even though we all like to believe out body knows what it needs, it's not necessarily true, especially when it comes to food cravings. Many people crave sweets, salty foods, fried foods and it doesn't signal anything. Cravings may increase during hormonal shifts, such as as PMS and pregnancy. Craving non-food like dirt or ice (pica) can signal anemia.
Sweets are addicting. The most common cause of craving sweets is eating sweets. After a few days of eliminating sugary foods, that craving goes away. Sugar substitutes won't help here; they may actually intensify the craving for sugar. After a week or so of no sweets, it may be possible to eat very small amounts of sweets without triggering the cravings.