There are many, many causes of labored breathing in general. For some examples: asthma, allergies, bronchitis, pneumonia, upper respiratory infections, heart conditions, fluid in their chest (multiple causes), viral infections, cancers....
Determining a cause requires diagnostics, starting with a physical examination and often chest x-rays.
Are you sure there are no emergency veterinarian's available in your area? I find very often in my area that people are unaware of the overnight / weekend emergency clinic that is open. I would do a thorough search online for emergency care options in your area and if at all possible get her in to be assessed in person asap. Labored breathing should always be considered an emergency until determined otherwise.
There are no at home medications I would suggest you try. In fact, any at home medications you attempt to administer could make things worse simply by stressing Peaches out.
Instead, the most important thing you can do for Peaches right now by far (that is, aside from getting her in to be evaluated on emergency), is to keep her in a calm, quiet, relaxed environment. A cat in respiratory distress that becomes emotionally stressed out will often crash extremely quickly. I'd suggest isolating her in a quiet part of the house, keeping the house fairly cool temperature wise, and possibly even lowering the lights a bit to help her relax.
Search your local area for emergency vets. If available, get her in asap. Also search for on-call vets, some do house calls. Treatment here will be dependent on the nature of her labored breathing and thus is highly variable, but initially she needs supportive care (e.g. oxygen therapy) and diagnostics. If you are absolutely unable to get her in on emergency, just keep things as relaxed as possible until regular hours open up again.