Hi and welcome
Please take a deep breath, first and foremost! Bring any outdoors piggy inside for observation and care.
You can place a bowl of steaming water next to the cage to help ease the water and keep your girl comfy and warm, but not hot.
You can find lots of practical care tips via this link here:
Emergency and Bridging Care until a Vet Appointment
Weigh her daily and step in with syringe feeding if she is not eating/drinking and losing weight. The need to breathe comes before the need to drink and only thirdly the need to eat. An antibiotic can additionally impact on the appetite. Keep in mind that over 80% of what your guinea pig should eat in a day is hay, which you cannot control by eye. You care in this respect can make a difference. Please never squirt any food or water into the mouth and give your piggy only as much as she can hold in her mouth and swallow - and that varies, depending on her size and how weak/strong she is.
Complete Syringe Feeding Guide
Weight - Monitoring and Management
Guinea pig airways are very small and narrow; they can also not breathe through their mouths, so every little obstruction in there is always very audible. Crackling and rasping are typical sounds for guinea pigs with a deep seating respiratory infection.
Hang on in there! The antibiotic should kick in within a day or two. Contact a vet promptly if your sow is suddenly getting worse with heaving sides when she is breathing and very apathetic, but please refuse any steroid injections; they are not suitable for rodents.
Please take the time to read the links I have given you. You will find them very helpful as they contain a wealth of practical 'how to' tips for caring for your piggy during a serious illness that I cannot all repeat just in a short post.