In the comics, Bullseye killed Karen Page, which means if Bullseye shows up in Daredevil Season 3, her odds of biting the dust skyrocket significantly, though not 100% guaranteed.
As for Elodie Yung, she may share similar sentiment since Bullseye killed Elektra in the comics as well.
However, considering that (SPOILER) Elektra was killed by The Hand in the Daredevil Season 2 finale, one would think that following her resurrection in The Defenders, she wouldn’t have to worry about being killed a second time.
However, it’s easy to deduce what Cox meant when he brought up Deborah Ann Woll’s “obvious reasons.”