Broo, the Elder Wand won't kill it's owner!! That's why in the HP movie, Voldemort couldn't kill Harry! So it would be so that Y/n couldn't have died either!!
Okay, the logic here though. I paused this at 5:00 to write this, so I haven't seen the ending yet. Voldemort says, "The Elder wand belongs to the person who k!lled its last owner. I must have the Elder wand, so Mattheo, go and k!ll y/n!" What's he gonna do? K!ll Mattheo after to posess the Elder wand? I mean, I wouldn't be surprised, but still. Mattheo went into this without questioning it. This makes no sense.