if you're working w/ other people there will always be 'drama' - some people are just more demonstrative than others. i agree w/ other comments - change of job - figure out if you like the making of food, serving the food or the management of it all - then either become a chef, a server (maitre'd) or business administration (or whatever your interest may be). maybe your place of business might even offer to pay for some classes if it helps w/ your job.
sounds like the lady actually is flirting a bit - but she's defensive, maybe cause of her weight - so she attacks first. you can try asking right out why are you so negative to me - she might not even realize she's being mean if that's how she's w/ everyone. good luck in all ventures!!!