Hi Annette - that is a really hard question. It really just depends on how long she is in pain for. It is different for all LO. If she is taking decent naps for you with this A time then don't stress about it. I knew plenty of mom's who had LO with that A time at that age so don't worry about it being too low.
When she starts seeming better than increase it again, or just wait until she starts taking longer to go down for her nap, or starts cutting the naps short again
Unfortunately I don't think there is much you can do to avoid it. Often it just happens when there is teething, and you don't know that it is causing the messed up napping until you figure out that they are teething

Sometimes they just seem to show the teething signs more than others and let you know they need to go down earlier.
HTH
