I would say at 3.5 don't worry about it, just let her swim.
I started competitive swimming at maybe 7, but I just did night trainings twice a week, competition night and the occasional swimming carnival on a Saturday.
for me I didn't start the early morning trainings (5.30) until I was about 12 and then that only lasted a short while as I hated getting up early tongue
From my experience it doesn't get strict until high school and that's only if the swimmer themselves wants to go further. I didn't have to change my eating or anything.
obviously its your call but just wanted to give you a point of view from a swimmer.
Thanks for your replies ladies.
DD does have 2 sessions a week with a private coach at our home pool, obviously it is not strict or early morning at her age, at the moment she just loves to swim but is excelling and i was thinking now she is a good swimmer shall i stop the coaching and just let her keep practicing or if we continue with the coach?
Thanks nadz im glad its not until high school it gets strict