At the moment she has 10 events. (You can check how many you have in stat menu.. Relationship stat is the event counter)
If you need a hint try clicking on her door for a "New event" button.
If you haven't seen 10 Amber's events and you still can't get a "New event" hint, try playing the other girls' events and it should unlock
Or you can also try telling the exact relationship level you have with her and I'll tell you what do you need to progress with her.