Rebdonial above quotes the Rambam (the sholchon aruch says the same wording)
I understand that you would have no issue with touching (not chibuk or nishuk) the older sister or the aunt. can you define keyotsah bahen. I was taught that means a niece. (similar relation as an aunt) from that Rambam a niece can be (technically) touched. not to say it’s a smart thing. (I like my arms 😉 )