Hi and welcome
Caramilk has clearly got some social issues due to her background even though your sows are bonded. The problem is more whether it is verging on bullying or not. Your girls are now teenagers in terms of development.
Learn more about behaviours and dominance:
Sows: Behaviour and female health problems (including ovarian cysts) (See especially the chapter about behaviour)
A - Z of Guinea Pig Behaviours (dominance)
Measures you can take:
- Consider getting children's stool to use as hideys. They still provide cover but are totally open and cannot be controlled like your current hut. At the extreme with very dominant over-controlling piggies, just a sheet over a large part of the cage and no huts can do the trick.
- sprinkle feed veg and pellets around the cage to minimise food hogging. Keep in mind that we just recommend 1 tablespoon of pellets per piggy per day and ca. 50g/one
small bowl of preferably green veg per piggy since these two food groups together replace the supplementary role of wild forage (not more than a quarter of the daily food intake). The more hay your piggies eat, the better for their health and a longer life. Sprinkle-feeding triggers their foraging instincts and counts as enrichment.
Make sure that you have access to hay that cannot be blocked and have hay and water bottles in different places in the cage.
Here is more information on a good diet, which can make around 1-2 years' difference in a piggy life span:
Long Term Balanced General And Special Needs Guinea Pig Diets
Use other enrichment ideas to distract Caramilk:
Enrichment Ideas for Guinea Pigs
When moving your piggies to a larger cage, you want to minimise a new bout of strong dominance as much as possible:
Please use bedding that has been short use by your girls, so it is scent-marked. Wipe all over the new cage and any new furnishings. Spread the bedding in the middle or if it is more than one piece, in different parts of the cage or let your girls have a romp through the new larger bedding in the old cage for a day.
Guinea pig groups are highly territorial and react to any changes in personnel or premises with a renewal of the the hierarchy that is at the bottom of ever group.
Working out whether you are dealing with a case of bullying or not:
Please weigh your girls once weekly on your kitchen scales (part of normal life-long health monitoring) but check for potential weight loss or a noticeably reduced weight gain compared to the dominant companion in younger piggies.
Weight - Monitoring and Management
For working out whether Cookie is feeling bullied and unhappy or whether the bond is still dysfunctional after tour improvements, please read the information and follow the practical advice in these links here:
Moody Guinea Pigs: Depression, Bullying, Aggression, Stress, Fear and Antisocial Behaviour
Bonds In Trouble
If Cookie turns out to be much happier on her own, please consider inserting a divider into your new cage and keep them as a bonded pair with interaction through the bars but their own territory. This solution is more common for fallen-out 'can't live together and can't live apart' teenage boars but it does work for sows, too.
What you can do for Cookie:
Cookie is very timid and likely rather stressed (i.e. having raised instincts) so please take the time to learn about prey animal instincts in guinea pigs and how to best avoid triggering them. Tell her that she belongs in your herd and is much loved in her own language.
Understanding Prey Animal Instincts, Guinea Pig Whispering and Cuddling Tips
How To Pick Up And Weigh Your Guinea Pigs Safely
Arrival in a home from the perspective of pet shop guinea pigs
All the very helpful and practical links above are part of our much larger information resource. They contain all the little how-to details and background information that we cannot write out in every single post. You may want to bookmark the link, browse, read and re-read at need as you can take different things from a guide at different levels of experience:
Comprehensive Owners' Practical and Supportive Information Collection
I hope that this will help you to work out what is going on and give you options if things are not going quite to plan. Your piggies are what they are and have been made by humans, our job as loving owners is to find what works best for them within our own means.