The Attack team knew that the black dragon was Pedro. But, they did not dare lower their guard and were prepared to fight back even if they would only be able to deal a scratch to the impenetrable scales of the black dragon.
As the dragon landed, Talia comfortably sat and leaned her back to the 'slightly' burned tree. Yojiro was concerned for her safety, but because he needed to keep his guard on maximum against the black dragon, his attention was shifted back and was focused on Pedro.
On the other hand, Mathew and Sabrina knew the reason why Talia is relaxed. In case that the dragon would attack them, Talia could just simply transform into her Ant Transformation and hid below the ground.
Spotting her would be difficult compared to the Chicken and the Eagle transformation of Mathew and Sabrina, consequently making her the safest amongst everyone else in the Attack team.