Urgh I HATE it when someone keeps bringing something up over and over again, that THEY deem as hilarious. I would be tempted to start saying you don't know what she's talking about/you don't remember it. I have done this when people do this.
My DH had form for this some years ago, laughing and teasing me for a couple of faux pas I did many years before. Still LOL-ing and dragging it up for cheap laughs 7 to 8 years later! No-one laughed except him, because it was almost a decade before! He doesn't do it now and hasn't for some years but it was annoying. He thought he was so funny, re-telling the 'tale' for cheap laughs at my expense.. I just kept saying I didn't know what he was talking about and changed the subject, and he eventually just stopped.
IMO it's borderline bullying when people keep banging on about something that you did wrong, or something you messed up, or some accident or incident you had (not that what you did falls into any of these categories.)
One woman I knew some years back had a DH who kept CONSTANTLY reminding her that she had fluffed her lines when they got married. Every opportunity possible, he brought it up and laughed about it. Usually when they were with other people No-one laughed except him.
She felt like shit when it happened, even though everyone said it didn't matter, and he kept bringing it up, for cheap laughs.. She went red every time. The 15th or 16th time he had mentioned it in 2 years, her mother yelled at him in front of 10 people (the 10 he was sharing her hilarious mistake with.) She told him he was a fucking arsehole for dragging this up constantly. 'Well I am only having a laugh' he muttered meekly.' YES, at HER expense you fucking twat!' her mum said. He never mentioned it again.
@Aboutafriend You really need to either say you aren't sure what she means (like you forgot) OR tell her to stop mentioning it because it's tedious now. If she persists I would be giving her a wide berth tbh. Couldn't be friends with someone like this.