Well, she did mention first that Bill did not wrap up his nomination until after California voted, she then went on to mention Kennedy being shot in June in CA. Whatever point she was trying to make, you know there are those in the Obama camp who will jump on this remark.
Doubt they'll make a big public issue out of this. They'll merely accept her apology and move on. (If they were smart, they might ask for more Secret Service protection behind the scenes.)