Yes. It is. It is an unbeliever deserting a believer, iirc.
Would a believer desert his/her spouse?
I was thinking originally of the passage in 1 Corinthians 7:11 in which Paul certainly appears to sanction separation for two believers, but commands that it must either result in celibacy or reconciliation. It looks like Paul’s acknowledgment that sometimes cohabitation isn’t working—as with the abusive spouse you mentioned. But if there is no adultery or desertion involved, then separation appears to be the Scriptural remedy.