Wow, a lot of interceding issues and complications in the OP.
Your friend is not doing anything blatantly against you from what I can tell. It seems to me that initially in your friendship, she was 'non-threatening'. Now, the relationship has evolved to where she is gaining some more self-confidence in her presence in the program, and you are envious of that. Her self-confidence could be coming attempts to compete with you, but more importantly, your perception is that the friendship playing field is no longer equal. This in part, is why you wish to know more about what is going on with her and her life. The perceived secretiveness about her life only fuels your suspicion that her actions within the department may have ulterior motives. Perhaps she does not feel comfortable discussing personal information to what are essentially co-workers. What she is doing is realizing what she needs to do to position herself favorably within and outside her department. It is obvious that a good work ethic, along with active participation in departmental affairs helps her in that regard. This is also something that you should do. Instead, you're letting your self-esteem and enviousness get in the way of your own progression.
As for your advisor, I can completely sympathize. Your advisor is undoubtedly the biggest influence in your graduate school career. The validation, or lack thereof, we receive from our advisors largely shapes our identity within, and in most cases, outside the program. One of the biggest things I've learned in graduate school is to seek multiple mentors; even those not in your department.
In a final point, you must...MUST...resist 'leveling' with your cohort mates. As you probably can tell, it is mentally nauseating to seesaw back and forth about what another person has or doesn't have (e.g., I keep myself up more, I have an official RA position, I have kids so I can't possibly be a high overachiever like this person, etc). If you and your friend got together and both of you threw all of your problems in a pile for each other to see, you'd quickly grab yours back. That's just the nature of life. You can only do the best you can do, especially when you have other more pressing obligations (children).
I would also not be upset about keeping your distance from this relationship. Regardless whether your insecurities are to blame, you should not be in a relationship where you don't feel worthy. Good relationships feel good. This is not just limited to romantic relationships, but to all of your relationships.