my professor keeps calling me by a different name

So this isn’t an attack on my professor or anything, I’m just genuinely confused. I just started my first year of grad school and I’m in a class that’s an elective and not required for my specialization. on the first day the professor asked us to introduce ourselves and i introduced myself giving my full name. since then, my professor is using a shortened version of my name when emailing me or calling on me in class (example: calling someone jackie who goes by jacqueline). it’s gotten to the point where my classmates are asking me if i go by the nickname i’ve been given or my full name. when i sign my emails to her i sign my full name, but when she responds she addresses me using the nickname. all of my other professors call me by my full name except for this one. i don’t know if it’s because she likes me so she’s giving me a nickname, or if it’s because she doesn’t like me. i consider myself to be a good student and a hard worker and i’ve never had this happen before. any thoughts? (please don’t attack me, im very sensitive if you can’t tell)