Your education/interviews/early career are adding value to your skills and remuneration, if you follow the most typical paths, each year you will make more money than the previous year - occasionally in small payrises, sometimes in big steps as you shift jobs to better ones thanks to the experience/skills/network you gained in earlier roles. This will mostly "just happen" unless you fuckup or sabotage it big time. It'll be the assumed progression for you by your managers, recruiters, lenders, partners, "the world".
Your cousin does not have that. In five years, you'll be well on your way to her $10k/month, if not beyond already. And you'll be wondering to yourself "are they gonna try and stiff me with just a single digit percent payrise here, cause I have a bunch of recruiter calls I'll letting go to voicemail I could start picking up on.." What's your cousin going to do when her admittedly valuable youthful beauty inevitably wanes? What's her $10k/month Instagram influencer income going to look like when she's 25? Or 35? or 50?
Be happy for her that she's taking advantage of what she's got. Be generous with any advice you can offer her about planning for her future, when some new pretty young things come up underneath her and leave her wondering where all that money went...