My boyfriend ex girlfriend is weird or am I tripping

My boyfriends ex added me on Snapchat & so I accepted & added her back to be nice because I’m not rude at all but I have this weird feeling that she copy’s everything I post. I screenshotted something my boyfriend posted of me on his Instagram & posted it on snap & 3 hours goes by she does the same. I post videos of use singing in the car having fun & her & her fiancé do the same exact shit like an 1/2 after I do & I have been investigating on my snap ill post something& see if she looks at my stuff & then posts somthing & she does && I just don’t understand has anyone ever been in this situation? Maybe I’m just tripping but I don’t know