Can an empowered Ambessa, The Wolf be targeted by abilities that kill?

Yes. Empowered Ambessa, The Wolf can be targeted by kill abilities — her Empowered text only stops damage, not targeting or destruction.

While Empowered she reads "I have +3 [M] and can't be dealt damage unless I'm in combat." That is a damage-prevention effect only (and "can't" beats "deal" for damage effects, Rule 54). A kill instruction like "Kill a unit at a battlefield" doesn't deal damage, so nothing in her text interacts with it — she can be chosen and killed normally, at 7 Might or otherwise, because kill effects don't compare against Might.

Two caveats: if the "kill" is delivered as damage (e.g. "deal damage to a unit"), she's safe while not in combat — only a Combat Showdown with her as Attacker/Defender counts as "in combat" (FAQ 12299). And if the effect says "all units at battlefields" it never targets her, so targeting restrictions are irrelevant either way.