I've seen that picture. There's nothing particularly shocking about it, or offensive. And this is coming from someone who is very easily triggered and known to make use of the report button when he sees something that is particularly shocking or offensive.

She has a right to be shocked, as we all have our limits, I suppose. And some of us are shocked easier than others. However, as long as you were not breaking any of Facebook's rules by posting it (once again, I've seen it, you definitely weren't) you are right in thinking that she doesn't have to look if it offends her. It's your wall, you're free to post whatever you want on it as long as it isn't breaking their terms of service.

Also, my answer is always The Man Who Sold the World.