There is no required level to do that.
What matters are your skill points (sweet talk and seduction) and knowing what pick-up phrases to use.
There are 3 lines to choose from and they work for girls in 3 different temper intervals. Hoover the girls pic to see her temper.
Temper below 34 use the top line, use the middle line for temper 34-66 and third line for temper 67 and above.
Always make sure the first pick-up phrase works, by checking the meter that shows the girls arousal.
At some point she will ask for a gift and you'd better give it to her or you will get dumped.
The CC gifts (champagne, high heels etc) are very effective and can be given soon as the gift option is active, even if you already gave her another gift.