Hi!
Please have her seen for cheilitis (lip infection) as soon as you can get an appointment and stop feeding fruit and tomato, which can cause tiny cracks in the lips and mouth through which bugs can get in; this can be bacteria, fungal spores or even a pox virus. Advanced cheilitis can be fatal. Some piggies seem to be more sensitive to acid foods than others.
Here is more information on cheilitis:
Guinea Lynx :: Cheilitis
Here is more information on diet. Please keep in mind that hay (and not veg) is the mainstay of a diet and should make around 80% of the daily food intake. Grass and hay contain both vitamin C and are the reason why guinea pigs never had to make their own vitamin C in the first place. Fruit, tomato and veg high in sugar like carrots and sweet corn should only ever be an occasional treat. Fresh herbs are a much better and healthier source of vitamin C and trace elements. A good general diet can add 1-2 years to a healthy life span and take a piggy from the lower end to the upper and beyond.
Our diet guide looks at all food groups in detail but as an overall part of a balanced diet. You may find it helpful:
Long Term Balanced General And Special Needs Guinea Pig Diets
Guinea pigs don't do playtime. They either belong to a group or they don't. Any meeting with guinea pigs that are not part of their group is an aborted bonding session, which is very frustrating for them.
Single Guinea Pigs - Challenges and Responsibilities
Bonding and Interaction: Illustrated social behaviours and bonding dynamics