Should I take it personally if someone deletes me on Facebook?

I worked in a lab for four months about a year ago, and six months later I added some of the people from there on Facebook. Most of them accepted (I had been friendly with everyone there, but I wasn't really friends with any of them as I didn't directly work with them or get too many chances to talk to them). I noticed one of them wasn't on my list anymore, and sure enough, when I looked up her name, the "Add as Friend" button was on her page, meaning she had defriended me. Again, we weren't friends, just more like friendly acquaintances - but my new boss collaborates with my former boss and is planning a joint project with him, and I may be going back to that lab to work a few times a week pretty soon (and see/interact with most of these people again). I'm not devastated or anything, but it's kinda hard not to take it personally when someone has deleted me. Should I be taking it personally?