Is it normal for a girl to be obsessed over a guy ?

My sister is doing a play this weekend she has a huge crush on a guy in the play. She told him the other night she liked him he smiled at her. She's only known him for a week. Her and her friend were going out to dinner tonight after opening night she invited him but he said he might have to work he's not sure yet. She's gonna ask him again tonight. She said when she's around him she gets butterflies in her tummy her heart beats fast her knees feel week she sits and stares at him the whole time he's on stage. She's nervous when she's around him or talking to him. She said she had a dream the other night that last night was opening night he gave her a good luck kiss in front of everyone she said it was embarrassing but cute. She said she has been dreaming of him every night this week. She dreamed about her and him either being married or dating. She is defiantly in love with him but she's so scared to tell him since he's older than her she's worried he might get mad if she tells him. She said she cried after she left last night because he's so cute. She seriously cried to sleep last night. She said she never felt this way about anyone. Is it normal for her to be obsessed over him ? She wants to know if the dreams mean something and if she should tell him she loves him ? She's 23 he's 30