I'd be pretty furious if she died on my game as well. Definitely my most used vendor in the game by far, mainly because of the location right next to Breezehome.
Side note, every time I come to the forums people are complaining about vampire attacks on cities. Not once I have seen this happen on two of my toons games. On one of my toons, he's lever 50+ and has completed the Vampire portion of Dawnguard. My other toon, level 14 and hasn't started Dawnguard. I may be the only one on the forums that wants to see an attack on the city. It baffles me that this hasn't happened to me yet.
For the 50+ character you will never see them now that you have completed the MQ. For your level 14 character it is still early. Plus, the attacks pick up dramatically after completing the DImhollow Crypt quest if you side with the DG. Until then I think they will be somewhat rare. From my understanding, you don't get vamp attacks, or at least not many, if you side with the vampires.
Also, the lethality of the vamp attacks can vary greatly. If you get 3 vampires they can be very dangerous. One vampire and 2 thralls, less so, but still a serious threat to the citizenry. One vampire and 2 death hounds are not too bad. (Since most of the citizenry are Nords they have 50% frost resist.) Single vampires probably will go down before they can kill anyone. I have seen all these combinations.