Nasty how - attitude, cleanliness or....?
Yes, a cow that is in the routine of being milked at particular time will be impatient as her body will be demanding relief of the pressure of her milk supply. A cow's behavior at milking can vary a lot from cow to cow - some are very "nice milkers" while others will go their whole productive life being "that cow" (I've dealt with both). The frequency of milking will depend on how you manage your cow. If you have a cow that you want for just a little milk for your family you can leave the calf with her and the calf does all the work for you with regards to keeping her milked, making it less an issue of having a routine milking schedule, etc. If you don't have a calf on her/want all the milk she gives to be collected rather than suckled you generally milk a minimum of 2x a day - but *could* milk more frequently if you wanted to (a calf would suckle more than 2x a day) and just had nothing better to do all day long.
In my experience all cows are so different they all have their own unique personalities. I only have one jersey, one milker, she doesn't like it. She has kicked me quiet a few times but I hand milk her. She was a heifer though so she is still getting used to the whole idea.
I have 14 in my herd right now that were bottle calves. They were all raised the exact same way. All but 4 are friendly. Why that is I have no idea but 4 of them are really nasty. I have 2 that are incredibly friendly and affectionate. They are just like any animal I guess. Some are just bad seeds and some are sweeties
Cows can have personalities the same as chickens or goats or sheep or any other animal. They also need some regularity to their routine as cjc has said. If you want milk, then milking needs to be done regularly. Doesn't have to be 4 am and pm, know some people that milk at noon and midnight. A calf will nurse frequently but a "dairy" cow will have too much milk for one calf as opposed to a beef cow that will normally only have one at a time although there are sometimes twins. There is mastitis to deal with if you do not milk the dairy cow at somewhat regular intervals. I have several that will nearly push you out of the way to get in the barn for their feed and to be milked and have one that you have to go out and make her come in. Some cows are friendly in the field, some are not. Doesn't necessarily have to do with how they are raised either. Some will come when they are called, some will look at you like "what do you want? or you want me to go where?"
Are you looking for a dairy cow for milk for your family? I know there are alot of Texas based folks on here but most have goats. I am in Va so too far away to be of much help. But @Latestarter is in Tx and @Devonviolet and they were buying milk from somewhere down there and it was off the farm I think....maybe they can help you out with a place to go see/spend some time around a dairy animal....