Hi, V.,
My favorite thus far, and by far, is made by THE FIRST YEARS. Ours have Sesame Street characters all around the cup. The top is durable enough to withstand chewing, there is NO valve, and it never leaks! I think I bought them at Publix.
I also liked the green inserts that work with Avent bottles. They are very durable and both my kids drank well from them right away.
Those take-and-toss cups are handy. They last forever and the spouts withstand a lot of chewing yet still work. (The top just snaps on, though, so your daughter probably isn't ready for them -- the top WILL come off when she drops or throws it to the floor.)
My son loves to chew his sippies, too. My daughter never did that I can recall. Some people are more "oral" than others, so your daughter very well may continue doing this, just because that's "her thing." I've tried lots of different cups looking for the easiest to clean/different kinds of valves, etc. My favorite are the ones with NO valve. (I appreciate knowing they are really clean, plus it's one less thing to mess with and keep track of!)
Good luck finding what works best for your Brittany.