Being calm is the state of not feeling nervous or restless. Contrary to that, being antsy means someone who is restless, not able to be patient or even wait for a bit, nervous for what is to come. So, when the sentence reads "Cole and Susan were total opposites. Susan was antsy waiting for the results of the test, while Cole was calm a a cucumber" it shows that Susan is restless and impatient for the results to be out.
Wallflower??? as in plants?? uhhh well there's a lot of species so it won't die out fast... i'm pretty sure this wasn't your question i'm missing something though lol
