One of my girls is 2 years old. She was housetrained by about 3 to 4 months, but this past week or two (whilst being in season) she seems to have forgotten all the "house rules" for piddling. She sleeps in the kitchen at night, and we got up this morning to several piles of pee. Its really annoying as to why she is all of a sudden doing this.
I have had the same problem with mine in season, I'm sure they cannot help it and they return to normal as soon as the season is over. You could offer some newspaper near the door to minimise cleaning up but I do not feel it is fair to chastise them.
There is no need to tell my girlie off lol, as soon as we came down and she saw the shock on our faces she put her ears back and sat there looking at us so sorry lol. We just put her out. There is no need to shout at them i feel when they quite clearly know what they have done is wrong.
I may nip her to the vet as her urine is very strong, but is drinking plenty.
Fingers crossed that it won't be a big deal - it could well be as Isabel said since she's lived with it before. It's just that I've not had that problem with my own girls during seasons so my mind immediately goes to things I've been known to suffer from myself :D