I’m sorry to hear this.
Please urgently step in and syringe feed her mushed up pellets or a recovery feed if you have it (oxbow critical care for example).
Syringing water and vitamin c will not keep her gut functioning. It is essential she gets fibre rich feed to replace the hay she is not eating for herself.
Switch from the routine weekly weight checks and instead weigh her daily so you can ensure you are syringe feeding enough feed to her in each 24 hour period to keep her weight stable.
She may only be able to take small amounts of syringe feed at a time if she is struggling to breathe so you may need to feed very frequently - every 1-2 hours for example, and aiming for 60ml of syringe feed in each 24 hour period - but it all depends on what the weight checks tell you, she may need to be fed more than that to stop her from losing weight.
The guide I will link in below will explain syringe feeding further.
I know it’s not as easy to get a vet appointment in the US, but could you try another vet or call for an emergency vet. Her symptoms sound very concerning and this cannot wait a week to be seen - if she is struggling to breathe, then she needs to be seen right now.
All About Syringe Feeding and Medicating Guinea Pigs with Videos and Pictures
Emergency and Crisis Care as well as Bridging Care until a Vet Appointment
Not Eating, Weight Loss And The Importance Of Syringe Feeding Fibre