Can I prevent my friend from seeing future updates on my Facebook Timeline?

[Mich]

We have been acquaintances for years but lately, she has been snooping around. She has been able to see whatever I have posted on my timeline and photos that I have been tagged in by myself or by my friends.Due to the fact that we have mutual friends, I cannot delete her nor block her completely from my past updates but can I block her from future updates? Will she know? Or will it appear to her that my timeline has been inactive, as if I haven't updated / logged in to Facebook for a long time? Thanks for answering!

[Stacy]

When you type something into the status box, there's a small circular shaped symbol just to the bottom right that says "Custom". Click on it and then on "Custom" again and it should say "Hide this from" and then just type her name in.