what to do

my eldest got in trouble yesterday in school we got a call from the principa; telling us that she was in the office because she hit aanother kid in the face. this is very unlike my daughter to act outlike this in school so we asked the principal what happened she told us there was a girl that was climbing on my daughters desk and "getting in her personal space" when she lashed out and attacked. the principal said the only reason daughter was in office was because while they were talking in th hall everyone was watching and daughter was embarrassed. but the other girl was also at fault.
when my wife told me this i said "good for her, what the heck is this girl getting in her personal space and i'm glad my daughter is able to defend her space like the mountaingoat she is named after.
my wife felt that it was not good for her to do that and i have to stand behind her and back her up in our stern discussion of the situation. i said of course she she shouldnt have lashed out (but i'm glad she can)
what do you think?
ADDENDUM:
it has been brought to my attention that people may get the wrong idea from what i wrote, my eldest is an exemplary student with no previous record of badness. she loves her trachers and her school and is very mild mannered. this incident is totally OUT OF CHARACTER and that is why i felt it to be newsworthy to find out what to do about it, not to spread evil things about my daughter. she seems to need more TLC as there have been numerous household changes in the past few weeks