I have read explicit things and did get caught by my sis, but she just shrugged it off as 'horny teenage boy' phase so I don't think that's gonna work for you.
Just try not to aggravate her since it isn't really illegal for teens to watch porn, but don't. I repeat don't try to explain anything.
You try to defend yourself: scolded.
You stay quiet: scolded
You try to calm her down: Might be excused from severe consequences.
Btw, my mom did catch me watching porn in 6th or 7th grade and exposed me in front of my dad and sis. I was ashamed and cried for like hours.
But I don't remember much since my immature self just got a few laughs from my parents who actually enjoyed seeing me cry.
Talk about sadists.
My mom caught me reading Yaoi, yes YAOI not Shounen ai. Goodness, please pray for me. Idk what excuse I'll make