@Light My vote goes to...
"Wait. We should get reinforcements in case this proves too dangerous."
That way, we can kill three birds with one stone: We can get her back to her master without resistance from Aika, we can gather more information on the dragon and why taking the heart is so important to Aika (and make sure that we won't be starting some apocalypse by releasing it), and we can ensure that Aika doesn't get herself killed by ensuring we have actually have reinforcements we can trust.
I second this. :)