The requirements for leveling Valentina up to level 6 are: 2 opera tickets, 4 mementos, 5 daily game tasks and 6 harvested crops.

Mementos gotten before getting to this level still count as I had gotten 2 earlier and only needed to get 2 more. As for the previous requirement I got past the high roller without actually maxing out the lust bar completly every time. It seemed to count a few times were I was only close to maxing it out. In achievemnts it count me as maxing it out 7 times and I'm pretty sure I have maxed it out at least once after I finished the requirement for Valentina.