My friends car stalled so she called AAA for a tow and they decided to try to jump her battery. In doing so, they "blew her electrical system" and now it won't start. I'm not quite sure what they ment by that because I heard about it third hand.

I haven't seen it yet but I wanted to check here first to see what can typically go wrong with a jump. Would it be something like a main relay that got blown or maybe one of the bigger fuses that protect the starter?

Thanks.
IRISH