Is this OK to say to a girl in the gym I find attractive? (she doesn't smile)

Seen this girl in the gym for about 4 times already. I noticed her glancing at me while she's running on a treadmill and while she's stretching yesterday and today. When our eyes met she doesn't smile then turn her head on the other side. I want to say hi to her but or smile but it seems she's not that approuchable. I decided to talk to her next time if I see her again. Girls, is this OK ?

"Hey, a favor. Can you smile for me? I want to see you smile. I really find you attractive, but every time I see you, it's like you're going to kill the person who will talk to you.( and il give her a smile) then tell her please don't kill me then laugh"

Is this cheesy? sorry for my English! by the way I will say this in spanish.

Just want to make it clear. I caught her many times staring at me and then she just turn her head down. I just want to be friendly and introduce her to the regulars there. Because I think she doesn't know what do in the gym.

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