I am quite sure that this thread was not at all helpful to you. I will try to make it even worse.
When I first started diving in Cozumel, it was in the summer. I always used a 0.5mm full suit, and it was just fine. When that wore out, I used a 3mm full suit, and that was just fine. In March, I would sometimes prefer a 5mm or a 3mm suit with a hood. I have two very experienced friends who always wear 7mm suits in Cozumel.
So there you have it. She should use something between a 0.5mm and 7mm suit, depending upon how she deals with the cold.
Hope that helps.
(FWIW, most people I see there use 3mm. I never wear a shorty because I want all my skin surface protected from things that sting.)
When I first started diving in Cozumel, it was in the summer. I always used a 0.5mm full suit, and it was just fine. When that wore out, I used a 3mm full suit, and that was just fine. In March, I would sometimes prefer a 5mm or a 3mm suit with a hood. I have two very experienced friends who always wear 7mm suits in Cozumel.
So there you have it. She should use something between a 0.5mm and 7mm suit, depending upon how she deals with the cold.
Hope that helps.
(FWIW, most people I see there use 3mm. I never wear a shorty because I want all my skin surface protected from things that sting.)