How do you choose a swimsuit size?

[ToetallyHeelarious]

DD13 is re-starting swimming lessons soon, and is quite self conscious about having to wear a swimsuit.
I measured her today as her current one is too small.
If I go by height she needs a size 32
chest - size 28
waist - size 30
hips - size 24

Surely the size 32 would be falling off her everywhere else, but anything smaller will be too short and uncomfortably tight over the body length? Am I missing something here?

ETA: I tried Decathlon's size finder and the results were "size not available"!

How about tankini types? I need seperate due to being completely disproportionate lol.

Can't, it needs to be a proper one piece swimsuit.

There are some sold in " long" which I buy as I am long in the body but as you say a size bigger falls off.

Take her to try them on? I took mine into sport direct which had loads in teen and adult sizes and she tried them on so we knew what would fit.

Just try them on.
Swimsuit sizes are a law unto their own.

Decathlon swimsuits come up very small.

I think I'll have to order a couple then and send back (hate doing that!) as our local sports shop had nothing vaguely teenager size and we won't be able to go to the next city until after she needs it.

@Pippsy which brands do long, I've never seen that in a swimsuit before? I wear bikinis....because I can never find ones that fit as my body is too long!

How about the tie back swimsuits? They are the most popular choice with the girls at our swimming club as they give a customised fit. DD1 likes Funkita and Amanzi, but I think other brands may do this style now too.
If you have to choose which of the various measurements to base the purchase on, I find body loop to be the best. DD1 can also span 3 sizes across body loop, chest, waist and hips.

Land’s End do their Tugless range of swimsuits in Long body.