I'd be inclined to try and get her spayed before she has a season, Leesy. The problem with waiting till she has a season is that once it starts, it's more difficult to try to get the timing right to get her in for the spaying before the next season.
We had Miw spayed at 5 months before she had a season. We were going to have Mouse spayed at 9 months......but then she came into season at 6 months, and we couldn't get the timing right to get her spayed because she was coming into season every 3 weeks! LOL! Spaying Mouse isn't an option now, with her illness.......but oh I wish we had it done before she got sick! Still in season every 3 weeks, and I SWEAR she must have some siamese in here.....the noise!!!!!
Maisy may well end up being like Mousie and coming into season every 3 weeks ALL year......best to get it done sooner!