I haven't gone through all of the posts on this thread, but what I will be mentioning is based off of experiences and observations I've had of women I've met or known of over the years who are like this.
I'm not sure if this was mentioned somewhere on this thread, but you being 30 I'm going to assume that she is a 20 something. Most women in this age range grew up with social media and if she is attractive it is very likely that what you are seeing is a bad habit that developed years ago simply because it was the norm when she was in high school. You have to realize that the amount of attention that these women receive on social media is addicting in the sense that they receive so much validation from it, after all only a select few are actually making any money off of this. Virtually all attractive women that I know of in my area post on social media, much of it being attention grabbing photos like butt selfies or what have you.
With that said, there is a big difference between blatant habitual attention whoring on social media vs. occasionally dabbling in it. The women that I know who were and still are attention *****s on social media had deep insecurity issues and a need for external validation. There was one that I met at my gym 2 years ago, I stopped talking to a while ago, and her whole instagram was her literally in little thongs, ass selfies at the gym, etc. When I first met her she wasn't too outrageous but after I stopped talking to her I noticed she'd always wear these over the top revealing outfits, like shorts barely covering her butt and junk. She made a habit of leading on tons of men, constantly rotated dates, would have a new semi steady bf for a month or 2 at the most and would quickly bounce to another.
Without making this post too long winded, this is what you should take home from this. Women like this have some deep seated issues that will only change when THEY decide to work on them. Combine this with the fact that our current culture is encouraging this type of behavior it naturally allows it to get to an unhealthy degree like you are seeing. Another thing to consider is that women like this usually have friends that are just like them, which again encourages this type of behavior. Many of the postings you see on a hot woman's social media are more from other women feeding into the narcissism, it's like a big circle jerk. As others have said, women like this are also usually very immature and not really wifey/gf material and really should just be a side chick or a one night stand.
If you really think this is something you can work out by all means try, but it's good that you are already catching this now instead of deluding yourself into thinking that this is healthy.
