If you've put on a significant amount of fat in your first 6 months, you've done it all wrong tbh. Eating too much for a beginner, you can gain strength and muscle just from eating at maintenance even if you're female. Never ideal to be cutting in your newb gains phase I say, but what's done is done.
Anyhow, when to start depends on when you plan to finish and how much you plan to lose. A caloric deficit of around 500 a day will see you losing about 1lb per week, 1000 a day for 2lbs a week and so on. So calculate how much you plan on losing per week (2lbs a week is a tad aggressive but perfectly healthy) against how much you're aiming to lose in total and when you want to be finished by, then you should be able to see when's the best time to start. Also, it's better to overestimate how long you'll need rather than reach the time you thought you'd be done and realise you're not quite there yet.