My friend is a deep sleeper that it's to the point it's a bit worrying

Like, you literally could have a very loud speaker beside their ears and they still won't wake up. One time, me and my other friends thought something was wrong with her like, she's sleeping like she's dead, im saying dead cos sometimes in her sleep she kinda holds her breath, like, for a few minutes, even when she's not sleeping and conscious she forgets to breath( many times she collapsed cos of that) idk how she forgets to breath but that's ALSO VERY WORRYING. Back to the topic, She's A VERY DEEP DEEP DEEP sleeper, even if we shake her up (LIKE A STRONG SHAKE) she won't budge, she's not even snoring , and then a few hours later she wakes up, idk if she sleeps at home at all cos all she does in school is sleep, im just hoping she's okay at home and nothing is going on, she hardly opens up cos most of the time she's sleeping