OP, she was excited to share her news with you that she had kissed a boy she liked and you responded by forbidding it, which was not a new rule, by the sounds of it. It doesn't sound like your rule got off to a flying start.
I think parents of teenagers have a choice: strict rules and something between lies and non-disclosure, or less rules and an open dialogue. I know which I would prefer.
What is it about 'dating' that you are afraid of? Historically, banning the relationships of others hasn't gone well. Might she be better dipping a toe in this world while she still lives with you and can ask for your advice? It sounds to me like she would. I imagine you have other rules to preclude things you wouldn't want her to do that might interfere with her studies etc.
I think secret relationships might be rather enticing for teenagers: Romeo and Juliet comes to mind. Your prohibition might make this boy seem really exciting. If she 'dated' him she might find it not half as exciting as she is imagining and you might get your wish.
I think when my time comes with DD14 who currently has no interest in dating because she thinks it's pointless at her age, I will let her handle it as far as I can. She's made really good decisions for herself so far and I trust her intuition. Lots of rules feels like a vote of no confidence in your kid's abilities to navigate their world.
This boy might have been imagining the odd kiss and a few messages as his interpretation of dating : the invitation to dinner might cause him to take fright and reconsider. Good for him if not.
Your DD sounds like a great kid, OP. Might you be able to trust her to manage 'dating' with you very much available for back up/advice?