Recently, our daughter (17 in June) told my wife and me that she has started dating not 1, but 2 guys. No introductions needed since we already know them; they’ve been close friends of hers for quite some time now. Daughter put it as: why do I have to choose if I like them both and they don’t mind sharing?
I just don’t like it.
You’re not a bad person for feeling whatever you’re feeling. It’s your actions that count.
I can forsee some potential issues with it but the worst that is likely to happen is heartbreak. And at that age it’s to be expected from just one boyfriend anyway.
She is almost an adult. Offer advice but at some point she will have to learn to live with the consequences of her actions.