Yes at a hobby. The instructor kept calling me a name similar to my own so I assumed she’d misheard (think Emily/Amy) and being really overly friendly with me. I was sort of reserved but polite as I was nervous and a bit anxious at starting a new hobby and can be a bit socially awkward at first. I couldn’t understand why she kept singling me out for jokes and things and saying “I know you can take it”, “you weren’t saying that in the club on Saturday night” etc. I felt really embarrassed.
It went on for a few weeks but she was getting more and more spiteful and angry towards me and had started giving me evil looks and clearly gossiping about me. She ended up asking me, at the end of the class, what time I’d got home on Sunday morning.
I was ??? 
“You were wasted when I left, what time did you get in from the hen do?”
????? 
I explained I wasn’t at a hen do at the weekend and I was on medication that meant I couldn’t drink alcohol.
She looked at the people she’d clearly been gossiping about me to for weeks and said “SEE? THIS IS WHAT I’M TALKING ABOUT!!! Whatever, Emily, I don’t know what your problem with me is!” and stormed off.
The rest of the class looked at me. One piped up, “I thought you were called
Amy..” and a few asked what it was all about. I explained I genuinely didn’t know and I really wasn’t at a hen do that weekend. I was really embarrassed and felt very awkward and was considering not returning. I went up to her and said very politely “look, I don’t know if you’ve mistaken me for someone else but my name isn’t Emily and I wasn’t at a hen do with you this weekend and I never met you until I joined this class x weeks ago.”
She was going “whatever Emily, I don’t know what kind of game this is that you are playing but it’s weird.”
It took a fellow classmate who knew me and suggested I show her my driving licence to go to her and say I was being truthful.
The following week she came and apologised and said “I don’t know what I was thinking, you don’t even really look or talk like her! So weird!”
She’d thought I was her former line manager. I googled her. We aren’t remotely alike.
I mean seriously.
What planet was she on?!