Thing is, IB can make poultry susceptible to other bacterial diseases such as e-coli and mycoplasma. Giving the vet the benefit of the doubt, that may have been what he was treating for (although Tylan would have been the correct antibiotic for mycoplasma in any case, not Baytril).
We really do need to know what this 'virus' was - can you perhaps call the vet and get him to refer back to your hen's notes?
If it was IB, there's really not a huge amount you can do to correct any damage she sustained to her reproductive tract, short of drastic surgery which I would not reccommend if the laying issues aren't causing her health to be compromised.
However, you can encourage more 'normal' egg laying by doing the following: make sure she is always well supported with calcium (a powder supplement such as Nutrobal given daily is very good for hens with compromised shell glands), minimise any handling of her (particularly in the early morning when she could have an egg forming in the uterus/shell gland), ensure she gets balanced nutrition and definitely avoid letting her get overweight, try and find a feed with low levels of soya in it (protein derived from fish sources is much better as it does not mimic the action of oestrogen, which soya protein does), and watch her very carefully for signs of egg binding (which is much more likely with soft shelled eggs), or eggs breaking inside her (she will need antibiotics/anti-inflammatories if a breakage occurs).
She should be fine in every other way though, if it was indeed IB, and as I said before, she cannot contract the virus again, although she, and any other affected birds, will always be carriers (and therefore infectious), so bear that in mind if you plan to bring new birds into the flock.
