customer got mad at me for being too nice

interaction was normal while she placed her order and paid, after handing her back her card along with her drink i said "bye thank you so much! have a nice day" with a smile. she then asked me "what was that about?" and i asked "what do you mean?" she then told me my energy was weird towards her and i asked her to clarify what she meant since all i did was say thank you.

she said my kindness was unnecessary and "fake" and i explained to her that we always try to give our customers the best experience possible.

she left but came back a few minutes later and asked for a manager's number, which she did not get since it's against our policy. gave her an alternative and she refused. she got even more frustrated and i apologized if i made her feel any type of way but she was still upset and basically threw a fit that she wasn't getting her way. so i told her to have a nice day lol.

three years as a barista, never had that happen. we've had issues with her in the past with other baristas.

edit: thank you all for hearing me out, this was a first time experience for me so its nice hearing everyone's takes and experiences with similar things! ima continue to make coffee and be my happy self <3