One of my yorkies, Kiwi, was highly allergic, and she had environmental allergies, as well. I know how difficult it is with allergies. I don't know if there is anything in Gas-X that Penelope would be allergic to. I gave her the baby gas-x because she had too many other pills to take, but the 1/4 tablet of the adult pill was prescribed for Ashley, and she was four pounds. She was a very active little girl at almost seventeen, and the vet said it wouldn't harm her. As long as you aren't worried about her being allergic to it, it is the same thing they give to colicky babies. I wonder if gripe water could help her. I didn't try it because I would have needed to check with our vet to make sure it didn't interact with Ashley's other medications. I hope you are able to find something to help Penelope.
http://www.colicshop.com/colic-calm-...pe-water.shtml