Saya’s route anime timeline is different with vn timeline though so it depend on which one you’re talking about.
VN version goes like this : Aya traveled with her dad -> went back to japan for the 1st time and met Riki -> travel again for roughly 10 years -> went back again for sometime and get into accident.
I think the only instance where Aya mentioned her age is at the earliest of her memories when she was 4 y.o so I’d say she was around ~14 y.o when shit happened.
Meanwhile the anime is this : Back to japan,met Riki,landslide immediately happen later that day.
It was Riki as he also remembers playing soccer with some kids in the neighborhood.
I’d say she’s alive in the anime since it gives way more hope for Aya,like the part where her father trying to find and call out to her when she was trapped in contrast to the VN where we only get to see Aya described about how she was going to die with no one come to help her and probably implied her dad also has it as bad as she is.