Is there anyway i can block one person from commenting on my status/photos etc?

I have this person on my facebook who i can't delete because they will get upset and also i have to see them all the time so it would be awkward. But they are so annoying they "like" everything i do and comment on it really strange stuff that they think are funny but really her sense of humour is restricted to herself i think. I also get like 20 notifications in the space of like five minutes because she just looks through all my albums and comments on stuff. She butts in in conversations and writes stuff that are completely off topic and the conversation always ends there lol. she only has 15 friends on facebook so she will know if i delete her plus she has problems with depression and she will take it to heart. i was wondering if there was a way i could prevent this one person from commenting on stuff and then if she asks me i can feign ignorance?