Hi there, Silvia! Thanks for getting in touch and welcome to the forums. 🙂
That’s a great idea. While it’s not currently a feature that’s available right out of the box, allowing people to RSVP, decline or show interest in an event directly on the site (with reporting) is something we’re definitely looking into. We recently updated Facebook Events to the latest Facebook API, and this is one of many things we’re hoping to add in future versions–though I don’t have a timeframe for when that would be available.
Does this help answer your question? Please let me know. 🙂
Cheers!
Geoff