Why do some people copy others in style and attitude?

All my life I’ve been copied. I had close friends and they turned out to be completely different after a year of hanging out with me.
I dont understand this.. they became just like me. even our lipsticks… there was this one girl i met this year, we became best friends and she changed A LOT… She even started wearing red lipstick just like I always did.
what i dont get is… i would never do that. I am and always have been me…
so, why do everyone else or at least MOST people do this?
dont they understand its pretty awkward since I CAN SEE her change? duh.

?