I was walking from Ivarstead to Shor's Stone when I discovered this farm. Two Dunmer ladies were talking at the vegetable plot, and as I neared it appeared they were arguing about something. However before I could speak to either of them a Blood dragon decided to pay a visit. The aftermath of the battle was that one of the women lay dead.
Is she imprtant? Are there any quests associated with this place? Should I reload and fight the dragon & try to keep both of them alive?

If they died they aren't important to any quests

One of them is related to a quest, but it is not an essential quest per se. Just a small side quest - one that links to a character from Oblivion, so it was interesting for me in any case.

If it was the younger sister that died, then it won't affect you getting the quest later on.

That's not entirely true, NPCs in minor quests are no always immortal in Skyrim.

They are somewhat involved with a quest involving nirnroot, but I think the quest can be completed without them. One of them also asks you to collect graqes for her.

Important to the Main Quest only, perhaps the Civil War. However, quest related NPCs can and will be killed off by the game.

So, yes, you may want to reload when an bystander gets killed by a dragon, or something else for that matter.

Hmm, I'm fairly sure faction quest NPCs are essential too.

Have not tried to kill one of those yet. I did have a Civil War NPC that is immortal, and this is after the Civil War is over too.