My girl went into heat around a week before her 2nd birthday. Not extremely common that it is that late, but not unheard of either. One reason I waited to spay her is the same reason you are. After doing the research, I have learned it is just a myth. Go get your girl spayed. Don't wait. I waited with both my girls. The first one had her 1st cycle almost on her 6 mo birthday. She ended up with a false pregnancy and that can lead to lots of other issues. So she was in having hers within a day of going to the vet for that. Plus the longer you wait the bigger she gets and the more it will cost you.
Pam, Mom to
Thor-male brindle 05/24/01
Arabella-female brindle 12/19/06
Star-at the bridge 05/13/98-11/22/08