Am I in the wrong?

OKAY so I work in a dispensary. Chill environment and chill people most of the time. This girl came in today was so nice to her. After her transaction she asked me if I was the only blonde that works here (thought that was a weird question) but I answered her saying yes. She told me that her boyfriend who is 34 (Im 21) says I’m flirting with him and I make him feel uncomfortable. “A little blonde young girl” in the bitchiest tone is what she said to me. I’m the nicest one there and the dude she told me he rarely talks to anyone when he comes in. I reassured her that I would never flirt with another man because ONE I have a man and two he’s just not my type. I told her I’m sorry I don’t mean to make him uncomfortable but I would never flirt with him because I’ve been dating someone for years now. She was like “Kay well keep yourself in check” at that point that got me heated because ONE who are you??? Telling me to keep myself in check. Second I never flirted him to begin with. So I called up my dad which is the boss and told him what happened and their names and he told me “If people can’t tell the difference between customer service and flirting then they need to go somewhere else and you’ve been in a relationship for years so why would you flirt with someone who’s way older than you” IMO I thought that was immature and insecure to come up to a business and tell me LIES. I thought she made herself look like a fool. And now it’ll be super awkward when he comes in or she comes in because of that. BUT I wanna know what you guys think.