Should I ask out my friend who's a girl little sister ?

[K.j.]

She's 17 I'm 18. She is my friends little sister and me her and my friend hangout a lot I really like her. I want to ask her out badly I've tried talking to my friend but she is a bad texter but she does know I like her little sister. So now I am thinking I should message the little sister on Facebook and ask her to go out with me and tell her I like her.

I was thinking of sending her something like hey I really like you a lot and I want to take you out on a date this weekend, will you go out with me!😊

Do you think that will work?if not what should I message her?

In all likelihood she knows that I like her because her sister knows, and since neither have told me know I feel like they are waiting on me to make a move. So should I message her that? And if not that what should I send her?