Interesting question if Sidir interrupts the Charge action itself, but is placed outside her charge range (ie more than 7" away) does Pandora still charge? His ability says he becomes the target regardless of range or LoS, but the charge can't be completed if she doesn't end within engagement range. In fact, she can't take the action at all. In which case, since Pandora couldn't spend the AP, could she then charge Sonnia (or whoever) again and since Sidir can't do it multiple times per turn he's SoL? Not sure there's a definite answer in the rules.