In my opinion, I can see why frequent posting like that - due to insecurity or not can be annoying. I just end up removing them from FB feed if I get tired of the same old same old posts (same with people who only post the same types of posts - clogs up the feed with stuff I don't want to see!). I'm only skeptical about that being a sign of insecurity because I know some people who do that because they are insecure and others who don't - they post like that and they are comfortable with themselves.
However, many of us are insecure and I know for me at least, I'm too insecure to even admit my degree of insecurity about a lot of things - physical, mental etc. As long as we are still nice people at the end of the day, that's what matters most. Maybe that person on your FB is insecure - if she isn't, that's great, if she is, then I hope that like all of us, she grows to be less insecure over time.