**Adding This:
ALSO, another thing I do with my kids is, instead of saying "NO" to everything, I simply say "stop" when they are doing something they shouldn't. Kids get desensitized to the word "no"....but if you say 'stop' it conjures up a different reaction in them. And they stop. If my son is across the room for example and is doing something naughty, I simply say "stop" or I give the sign language for it holding up my hand... and he knows instantly to 'stop.' No need for yelling across the room and saying 'no' and then explaining everything and getting ignored. Many times, I will say his name to get his attention, then I point at him and say "stop. now." and then he will. Versus if I say 'no' they just act like they don't hear you. Ha, ha. So I have found the word "stop" to be more useful many times.
You could try and teach both twins, sign language. That way, they have a way to communicate... teaching them functional words/signs for things such as: help, more, hungry, stop, happy, sad, milk, eat, etc.
But at this age, it's common that they bite. Some even hit and slap and pull hair. It's developmental and exploring. Certainly, they won't be fully cognizant of "our" rules. So, just keep in mind the age appropriateness of whatever method you use. Usually at this age, it being distraction and redirection methods. Yes, time outs are too much too soon. Or, you could try a 'time-out' for the toys... meaning, taking the toy away for a moment... if she bites. Then when she stops, PRAISE HER, and give the toy back.
It's also common at this age that they laugh and think it's 'funny' when they get told 'no' or scolded. Again, it all has to do with ages and stages and the developmental ability of the child.
Main thing, is not 'expecting' a child to be and act older than they are, and to expect said reactions to be more in line with an older child. Versus just a 1 year old. Expecting 'more' than what is indeed age appropriate, will only lead to frustration for Parent. At this age, your daughter IS acting normal.
A great book is: "Your 1 Year Old" which you can get from www.amazon.com Its a real easy fast read, and simply explains a child's age characteristics, and so that they parent can understand and know their kid is normal and ALL kids do things like this.
I would again, teach them sign language and 'manners.' Simply saying "please..." and "thank you...." and "your'e welcome..." for things. It's also 'modeling' for your kids, what is appropriate or not. But again, it takes time for the said behavior to sink in... so be patient. Things like this are not learned auto-pilot... and it takes a whole childhood to learn 'our' ways and rules.
My son also laughs and thinks it's funny when we scold him for hitting his sister, on purpose. We do the 'toy time out' with him, and this works. The key thing is... see what makes your child tic. For us, scolding or saying 'no' does not work with my son. But if we explain to him and describe 'why' something is not okay...then he is more prone to behaving in the way we wish. Which is understanding that hitting 'hurts' others and that he then 'apologize' to his sister and hug her. Then we always praise him for the desired behavior. And not giving attention to the 'negative' behavior.
All in all, this is normal for kids this age. "Parents" magazine www.parents.com also gives good run downs of what to expect at each age. And how to handle it.
Kids at this age are also starting to assert themselves and have a sense of self... so 'helping' them to handle things positively and while allowing them to explore themselves and situations are a balancing act. They are ALSO developing more 'emotions' which they never had before... so all of this combined, is a doozy for them. They simply do not know how to cope or handle all the feelings they have. So, we need to teach them. Just like a coach teaching a child how to play a sport.
But I would utilize sign language. Even if they do talk, or not at this age... it is real handy and useful for a child. Both my kids really benefited by it. AND... in tandem with that, teach them the 'names' of feelings, and the emotions... and empathy. Even if they are a bit young to completely understand it now... through repetition, it will be learned and they will understand in time. I did this with my daughter, and before she was 2 years old, she was very articulate for her age, in regard to feelings and what the reactions are in others, and could tell me the exact words for what she was feeling. :)
Also, their attention span at this age, in conjunction with their memory... plays into it as well. So, if she bites...you have to have a related reaction to it right then. Not 5 minutes later. By then, its too late and they might not make the 'connection' to why they are being reprimanded for something later. And yes, then they walk away. Their mind is simply on to other things by then. Kids get distracted easily! :)
Anyway, just some ideas. Hope it helps.
All the best,
Susan