I'm a little confused.
For her top in that picture I wouldn't use a spandex bodysuit at all - it won't stay up on its own no matter how many seams you have, it will be thin and floppy and deform a lot.
If you want to use the spandex fabric, I'd use it over a layer of sturdier fabric so that it will actually stay on and not lose its shape. I would probably look at "bustier" patterns or even use the duct-tape method to make your own pattern the "easy way" from scratch !
If you use spandex with no base you need to make a "breast plate" out of Worbla or something and glue/tack the fabric to it - otherwise you're going to get mono-boob. I'd personally rather use a sturdier under-fabric and make the top part have "cups" instead - the design is such that you could even make it have shaped cups with just the white and purple fabric if you used a sturdy fabric throughout the costume as the top layer.
As for the two patterns you have, there HAS to be seams on the second one. Unless you're custom-knitting something from scratch it needs seams since you're making it out of a big rectangle of fabric and sewing it together.
If I wanted to keep it spandex, I might suggest using a bra built-in to the costume so you could shape it over that. I would use at least side seams - but I would ideally want to make my own pattern for this since it's not a body-suit type garment. If you've never made patterns before look for "duct tape corset pattern" - it will show you how to make a pattern without having to know how to draft one - you just need someone to wrap you and scissors.