Terrifiying Threes

Forget about the "terrible twos"... Maya is almost three years old now and she started throwing temper tantrums. She also says "No" all the time, along with "I don't want". When I ask her "What you don't want?", she answers : "Nothing!" Everything is "No!' and "Don't want!', she tries to do everything in her power to annoy me. She doesn't want to eat, or she wants to eat something that she knows she's not allowed to - like, for example, ice-cream for lunch. When we shop, she runs away from me, throws herself on the floor if I try to pick her up, screams and kicks...I always try to keep a poker face, not to get to steamed up about things, but eventually I end up crying...
On top of that, people keep calling me "grandma". I know I'm not a spring chicken (I'm 43 years old) and I know that here people get married young and women giver birth to kids when almost adolescents, but from here to be called "grandma"...Israelis are soooo impolite. Today I simply exploded when I shop assistant (eating sun flower seeds at the counter) called me grandmother. He told Maya:"Luck what nice things grandma bought you..."So I stopped and asked him (with a smile that would make a freezer proud):'Look at me! How old do you think I am?" He starred at me, blinked and said:"Ermmm, fortish...?" Me: "Yes, I am forty three...and why do you think at thins age a women cannot give birth? This is my daughter, you idiot..." abd I stormed out from the shop...Never ever in my entire life was I so nervous, I was shaking...I am usually a polite person, almost shy. But that guy trigger a reaction, that reply was something waiting to happen for some time now.
Oh, and maya is watching now "Lazy Town" that's why is so quiet in the computer area.
One more thing. English is not my mother tongue and I really try to write correctly and everything, please do forgive my mistakes. Any observations are welcome. I am happy to learn (although 43, so bound to die any moment now).