To: It’s awesome but how do I know she won’t tell?
Me: Have to trust her not too – or she gets pregnant, when someone is going to find out sooner or later anyway – better to get her on the pill and you keep them and provide them to her, whenever she needs to have the next one and then she won’t get pregnant and much safer for you both.
You have already crossed the line, buy her small gifts or toys that her parents will accept from you and it won’t raise their suspicions.
She might turn on you later on, but if you keep her satisfied, s*******, you will probably be OK – nothing ventured nothing gained – and as long as she is close family and remains that way and you are her favorite uncle, what has she got to gain by turning you in, sort of thing?