Is this normal?? do any of you have "sisters" like this?

okay so i have a 13 year old sister who freaks out about like every girl thing! she is a major tom boy! it is rediculous! she somtimes gets mistakin as a boy when we go out to eat! that is rediculous! but she freaks out when she hears me and my older sister talk aobut cute guys or puberty or bra and all tht stuff! its really anoying! like the other day when my older sis way sorting the laundry she came across a bra and she was like tay is this your or alexes? and i was like its alexes and we look over to alex and she was red and was like getting up for the door in a panic! she does her own laundry casue she doesnt want any of us to see her underware especilly our brother! like we can tell what week she is on her period cause she doesnt talk to anyone especilly not guys! idk what to do... there is somthing wrong with her me and my sis and girly girls and she is looks like a guy literally! what should i do? btw im 16. any ideas?? any of you have a sister like that???