Sibling contact

I am the older sister of three siblings who were adopted by another family eight years ago. One of them is old enough now to be on social media, and I've found her but haven't reached out. I believe she would remember me, but I'm unsure if I should make contact. Our parents' (my dad, their mom) did not voluntarily relinquish their rights and because of this, the kids do not have to be given any information about their birth family. (I don't know what the rules/laws are word for word regarding this.) I was promised contact with my siblings from the adoptive mother but never received anything more than a picture the first year. My sister is 14 now. I am 26. I've been waiting all these years, and to finally find her was indescribable. I really want to contact her, but I am afraid she is too young or that her adoptive parents might become upset and try to charge me with stalking or something??? Does anyone have any advice? Is it too early? Am I breaking any laws? Should I even try to contact her at all? Thanks.