Hi and welcome
I am very sorry for your loss. 7 years is a great age but it makes the loss not any easier after all this time.
Here are our tips for what you can do for the bereaved companion immediately and in the longer term. As long as your remaining girl is eating and drinking, you have a few weeks' time to sort things out and do not have to find new company instantly; this should help you setting up an adoption. If your old lady prefers her own space, she will still profit from next door company for stimulation and interaction.
More practical and detailed tips in these links here:
Looking After A Bereaved Guinea Pig
Human Bereavement: Grieving, Coping and Support Links for Guinea Pig Owners and Their Children
If you can, please consider rescue dating with a couple of younger sows or a mixed pair.
Unfortunately, there is no rescue quite nearby but East Peckham Guinea Pig Rescue or April Lodge in Sandwich both offer dating and operate to a good standard, and you and your girl will be in safe hands there.
Here is a closer look at the various places you can get guinea pigs from with tips on what to look out for and what your customer rights are as it is a bit of a minefield out there. The guide also explains rescue dating:
Rescues (Adoption and Dating), Shops, Breeders or Online? - What to consider when getting guinea pigs
PS: You have unfortunately accidentally registered your postcode in a publicly visible place. For your own protection, please click on your username on the top bar, go to account details and scroll down to location. We would be grateful if you replaced it with your county so we can still give you information relevant to your area but without you exposing private information. Since we have members and enquiries quite literally from all over the world, it does help us to tailor any advice and recommendations to the country or part of the country our members are in with just a quick glance to the left.