[Petunia's been sticking to the fire ever since the first day, so when Lavi moves on over she immediately notices, brightening a little because hey it's the magic guy, before taking in his expression and the fact that he looks... sick?]

[And whatever doubt she has in her observation skills vanishes when Lavi starts convulsing]

H-hey!? [her first instinct is to jump over the fire and away, but what if he falls in while he's convulsing oh no, so she scoots on over towards him, reaching out but unsure on where she should touch him--] What's wrong?! Why are you -- did you eat something weird?? Did you get bitten by an animal?!? [but more importantly] Can I touch you?? I'm going to touch you okay!?

[she's more than a little freaked out, but she also doesn't want to grab his arm and re-open a horrid bloody wound of some sorts, so her hands kind of dance about -- trying to find an okay place to hold him]