That's so funny! My DD is like that too. We have to safety pin any bottoms over about a 4t. We have trouble with one pieces (and leotards) too due to a longer torso.YG
YG (age 9) can STILL wear her 4T and 5T bikini swimsuits... but the tankini top of her 5T shows off her 6-pack. The year I bought it, we were upgrading from a 2T... which STILL actually fit her, but the material was too thin. Her new one is a 7/8... but I had to put tucks in the shorts to keep them up.