User blog comment:SoulRise99/5 Things Alvarez Empire Arc Shouldn't Have Done/@comment-30852806-20170529190109/@comment-7418318-20170530212654

Remember that all of Zeref's creations are linked to him and will die too now that Zeref is dead.

Unless Lucy manages to sever this connection, Natsu will die. But if the connection is severed, it will almost asuredly also get rid of any Demon powers that Natsu has.

So either way, Natsu won't be able to use whatever it was he subconsciously used against Dimaria... if it was anything special in the first place, rather than the already established mechanic of opponents who are sufficiently more powerful than the caster not being affected by the magic of the caster.

Or maybe Dimaria just couldn't sustain her power for long on account of being beaten by a God Slayer and spending the "recovery time" in magic-sealing shackles. With her power I owuldn't be surprised if this was the first time she got seriously injured and thus didn't know the consequences.