Kale should be kept limited to one small amount no more than once per week. It contains a lot of calcium and too much calcium can cause bladder stones. Please cut it right down. Pellets and unfiltered Drinking water also contribute most calcium to the diet so keeping pellets limited to one tablespoon per day and filtering their water will help calcium intake reduce greatly.
try scatter feeding veg and pellets. It will mean they exhibit natural foraging behaviour, keep them occupied and it also means that both piggies get their share. she doesn’t know she is eating both portions, she doesn’t know some of it is meant for the other piggy, so spreading it all around the cage can help.
please don’t do anything to try to reduce weight gain. You also should not do anything to reduce her weight. Feed a good hay based diet with 50g Of veg and one tablespoon of pellets per day and that is fine.
please see the guide below for further information on how to check a piggies heft. It is much more useful to know whether a piggy is a good size for themselves rather than going by their weight. As there is such a wide variation in what is healthy , you cannot go by weight alone.
Weight - Monitoring and Management