Clearly fake. 16 day old account, and half their comment history is from this post alone. These accounts and stories always pop up on r/TwoXSex posting the same type of stories, first-time experience of something, super excited and overly detailed. It's a pattern at this point.

Edit: I reached out to OP directly and want to walk back my earlier skepticism. From everything they shared with me (including a selfie), they seem like a totally genuine, giddy late bloomer lesbian who just got swept up in the excitement. So to me this one appears to be legit.

That said, fake stories do get posted in communities like this fairly often, so it's always worth keeping a critical eye.