Obsessive friend

my friend of over five years is becoming obsessive. Worryingly obsessive. For years they have copied me (oh the stories I have to tell- in one instance I had legally changed my name due to safety reasons and with in a few weeks they were doing the same. Mind you they had never thought about it before then and suddenly it was like an itch they couldn’t scratch) This behaviour was bad enough and made me have a meltdown in my kitchen over how suffocated I felt. Yes, I had confronted them many times, but they always denied it. Back to my first point. I’ve noticed recently how entitled and overbearing they are towards me. How jealous they of everything. Possessive almost. If they see me speaking to another friend on social media, they will COPY my comments and send it to their own friends so that we speak exactly the same. They mirror the way I speak so much that I deliberately misspell words and they of course go along with it and use it forever more. When they do see me speaking with other, they become irritated and make passive aggressive comments or “jokes” about how they have me “all to themselves” or that I don’t need them anymore. I’m worried to speak to anyone in fear of upsetting them. They feel entitled to know EVERYTHING that’s going on in my life, down to the smallest of matters. If a family member moves house for example and I don’t alert them absolutely immediately, they ask why I didn’t tell them. (I’m a private person anyway, but my family’s business is no one else’s) if I go to the dentist, they need to know. Because that’s what “best friends are”
Those phrases or habits we all have that made us individually unique? You guessed it, that becomes their thing. I get a new tattoo? So do they. New pair of socks? Yep, the exact same pair will be on their feet within days. Any romantic interest with another and they go off the rails and often give silent treatment or comment that I’m theirs. They’re bisexual, so there could be romantic feelings there and they do flirt in a jokey way a lot. Either way you guys, I don’t know what to do.