Agreed--it's odd she didn't walk around with it. I surely would.

Two, Graendal managed to beat Moghedian and "Cyndane" at the same time. Girl's skilled. Second, we've been shown that shield's aren't just about power, but also cutting strength. If Aran'gar wasn't holding the Power, she could've easily shielded him. And then in the next second she was gone and he was balefired. Even if he could've broken through, that extra second would've been to much. If he did hold the power, so what? It was a powerful, quick strike from Graendal, who I repeat, managed to beat Mog and Cyndane at the same time. Compulsion, I believe, has a lot to do with Spirit, and it'd make sense for Graendal to be strong in it.

Sure, she may have an angreal, but I don't think that's an indicator of anything. Mog just wasn't as good as Graendal or Lanfear. Graendal, nor Lanfear, NEED an angreal to keep up--even if Nynaeave DOES have an angreal!

I point you back to the battle during the Cleansing.

Alivia had the finger ring angreal. An angreal that--well, there has been some seemingly contradictory info on it's strength. Nevertheless, we can safely say it at least doubled Alivia's power. Not only that, Alivia had other ter'angreal, such as the one preventing direct weaves.

Furthermore, let me remind you that Alivia is, by the Aes Sedai's own admission and especially what we saw from inner thoughts of those in the White Tower during the Seanchan raid, are better weapons.

So, Alivia, a better fighter than the AS and even Nynaeave (and slightly stronger than Nynaeave--I'd say Graendal level), with angreal, wtih ter'angreal to prevent direct weaves, went against an unaided Lanfear.

AND NEARLY DIED.

DAMN. Lanfear was sorely outpowered, the majority of her weaves wouldn't work, and she still won!

But...

Now Graendal has an angreal. And Alivia ate some humble pie and learned what it's like to fight a Forsaken.

If anything, I'd say it's gonna be Graendal versus Alivia. But, that's pure speculation.

The bottom line is this:

Graendal doesn't need an angreal to face down Nynaeave, even with the "battle gear". And even if she did, it'd be very easy for plot reasons for Nynaeave simply not have that on her during such a confrontation.