Is Ambessa 6* worth it?

I have one Noxus cristal and can upgrade Ambessa or Swain, really like them both.

I know Swain is really strong, but I like Ambessa's gameplay more + she isn't weak either, it's only a matter of building the right deck/having luck finding good items. I've beaten Lissandra with her at 3* and only with a common relic.

Since Swain is already strong without it and Ambessa's 6* seem strong (in theory, at least), I was wondering if it's a waste of resources or not to invest on her.

Can her 6* deal with harder adventures (deadly modifier)?

(Don't have the signature relic for any of them)