Rabbits can transmit diseases to G-pigs. Also, rabbits have been known to knick a G-pig to death.
I have only heard of one person who has sucessfully littler box trained her pig. I have not been able to, I have four of my own, and have rescued about 5. So, sorry I could not help you with that part.
Try feeding veggies only once a day. Wait till the pig has had its fill, then remove the left over veggies and feed only pellets and hay for the rest of the day. Make sure that the veggies that the pig gets are full of nutrients. No iceberg lettuce
! Plus, make sure you use one of these brands if you are in the U.S. : Oxbow, Mazuri, Km's pellets. Stay away from Kaytee or Nutraphase brands. The have a cancer causing additive in it. It is called something like: ethonyxine (sp?). Those pellets are not nutritionaly balanced anyway (despite what the bag or pet store person says).
What kinds of veggies is she giving?Here are some ideas:
Veggies: feed min. 1 Cup per day. Examples of veggies that can be given every day:
Give leaf lettuce: red, green, curly endive, romaine (no iceberg), bellpeppers, cilantro, swiss chard, grass, 1 cherry tomato a day, 1 baby carrot.
2-3 times a week: Kale, dandelion greens, broccli, mustard greens, beet tops, beets, fruit, bok choy, cucumber, radish.
You can visit GuineaLynx for a complete list of veggies and friuts. http://www.guinealynx.com/diet.html