Sometimes a bladder flush can help to relieve the bladder sludge, but it really needs to be done by a knowledgeable vet, otherwise it can be fatal if the water is injected too forcefully and backs up into kidneys. I have seen several piggies on the forum suddenly die within 10 days of a bladder flush, but my Cariad had several successful ones by a specialist, which helped her to live another 2 years. If your vet is not confident, I wouldn't push for one.
Ideally, you give her as much fluid as she will take in one go to help flush out the bladder. if you syringe, please never give more than 0.5ml (half a small syringe full) in one go; this is about a mouthful. Wait until it all has been swallowed before you give the next lot. You can try and flavour the water with a bit of pureed veg or grass if you think that helps.
Please split the medication and give twice daily. You can up the metacam if there are acute signs of discomfort and pain. Give probiotics about 1-2 hours after the antibiotic. Ideal is avipro plus, as it doesn't contain any extra calcium. The baytril is likely to not make much difference, as you are dealing with an inflammation.
http://www.theguineapigforum.co.uk/...vitamin-c-overview-with-product-links.115404/
I would strongly recommend to look at protecting the bladder with a wall coating agent glucosamine or glucosamine based products like cystease, cystaid etc. (which is a food supplement for cats, but can be used for bladder piggies and be ordered prescription free online from several providers).
For long term treatment, I would look at a strictly low calcium diet, which includes low pellets and filtered water to minimise a further build-up.
We have got an example here, but you can also just restrict your piggy to the veg cited as "daily veg" in the balanced diet thread.
http://www.theguineapigforum.co.uk/threads/low-calcium-diet-for-bladder-piggies.105930/
http://www.theguineapigforum.co.uk/threads/recommendations-for-a-balanced-general-guinea-pig-diet.116460/