Daughter is causing problems & arguments between my husband and I! Advice?!

I am 47 and have been married to my husband since i was 20yo, We are from & live in Italy, together we have 4 sons & 1 daughter. Our daughter is 20 and she is the apple of my husbands eye, She is a very beautiful girl & comes from a wealthy family and uses that to her advantage, She has had many boyfriends in the past & he never approved of them and they we're terrified to get on his bad side. A 28yo american musician guy is interested in her & can be all over her, Im personally not crazy about him but she is playing games with his feelings which i don't approve of her doing at all. Part of my husbands business is named after her, She is very use to her own way and has her father wrapped around her finger, anything she ever wanted he made sure she got, My husband has always been very protective of her, He also has a very strong personality, can be very arrogant, you could also call him obnoxious & very outspoken as he is not afraid to say what he really feels. She has decided she wants to move to the US and my husband is furious as that they guy that has feelings for her is trying to take her away from her home, My husband wants her to stay in Italy and eventually marry someone from her homeland, She traveled europe at 18 and he was always worried about her and sending her money. Many of her friends speak english & when my husband is talking to my daughter if her friends are there he only talks to her in italian or in general he refuses to speak to her in English. He is a very proud man and would give her the stars if he could, there is no limit to what he gives her but our daughter is very hard to be tamed & stubborn like her father and we have had arguments about her many times. Any advice on how to handle her & the arguing?