Now, before you think I'm crazy and not making an ounce of sense, Listen to what I have to say.There are people in successful and happy relationships with their younger sister's friend, and their sisters are okay with it, But your own sister in particular might not be okay with you dating her friend.
She could also be feeling protective of her brother’s feelings; telling her how that you really care about him can make her feel better. Agree to not do any major PDA in front of her, in case that grosses her out… Promise her that you’ll set aside time for just you two without her brother being around, because she could be worried that she’s going to lose you to him.
I like her and she's got some of the qualities i desire. But honestly, I don't advise dating your sister's friends. In case you quarrel who should your sister support? No there's nothing wrong in Dating your younger sister's friend.