If your neighbor asks you to house sit and water the plants and you kill one plant, does that mean the friendship is over?

I never claimed to have a green thumb when she asked me to house sit and water the plants. I really didn't think I would kill any of the plants. However, the one grass like plant seemed to die on my watch. In my defense, I don't think it was anything I did or didn't do but rather lack of sunlight. But, she probably won't think of it that way. She'll probably think I'm irresponsible. Sigh. If you asked someone to water plants and they killed something you'd managed to keep alive...wouldn't you re-evaluate the friendship? I'm only bothered b/c we have very few "friends" here and would like to keep the ones we have. I hope the plant didn't hold any significant memory to her. Also, should I email her ahead of time and let her know? What's the etiquette here?