16 year old dumb teenager crushes on someone older than them. Also water is wet, sky is up and earth is down, more at 11.
You def reading a bit too much into the entire situation. Given that Garment havent shown any real signs of answering Flechette's crush somehow it will most likely remain just that, a teenage crush. And even if it develops into something - which I honestly doubt given Garment's unique mindset - how the hell anyone could charge Garment with something if she never clarified just how old she is? She can claim she is 17 and lawyers would shrug and wave it all away, cant exactly prove that she lies. But again, that is assuming situation even goes somewhere. Literally everyone in the Forge sans may be Aisha (solely due to age) have better chances to start relationship than Garment. Including JOE.
Also also. Canonically she starts dating, what, 22 year old Parian and goes as far as defects to villain side. Its entirely on-brand for Lily. I guess she is hornier than average teenager or whatever.