From what you're saying, I recommend to just remove her from your trusted list of your personal profile. It's like a friend asking you, "Can I carry your wallet?" Maybe you have some photos on your profile that you want her to see but I can't really think of another reason she would need to remain on the trusted list of your profile. My wife is on my trusted list in case a meteor lands on me unexpectedly and I should meet my demise, she could at least open the privacy level and put R.I.P. or something like that on it! :D
Also, if you are getting your cousin's personal profile activity feed it sounds like you must be on her profile as a manager. That's also not best for her sake. Works both ways! But honestly I'm not 100% sure on this point about the activity feed.