It gets better!!
Thank you ALL for your responses...even to those of you who are experiencing the same thing with your puppy. It makes me realize that I'm not alone, and it's normal boxer puppy behavior! RockyCody, it DOES get better!! I tried the same things you did...muzzling her with my hand made Lillie go crazy, too!! She would bark and growl and come after me when I did that. I have been walking away from her (yelping seems to get her excited also!!) and it's starting to sink in...FINALLY!! It's only been a few days, and although I know it'll take a lot longer to actually get the point across completely, she is responding to us walking away and/or going to another room and shutting the door behind us. She cries and whines, too, but that lets me know that she is disappointed and wants to be with us!! Many times she just starts playing too rough again, so we repeat walking away. After a while, she gets it and calms down. I've also removed HER instead of us leaving the room. I put her in her crate and she quickly calms down...often falling asleep soon after. I think she's just overstimulated or tired when that happens and needs a short nap. It's not affecting her feelings about her crate...she still goes into it at night and doesn't cry. If I thought it was giving her a negative feeling, I wouldn't put her in time out in it.
I have to say that I was getting really frustrated with Lillie, too. I was beginning to not enjoy having a new puppy around. But, after learning her personality and seeing that all she really wants is attention, I'm falling in love!!! She is still too rough for my 3-year-old to play with. My daughter gets too excited and that carries over to my puppy...who, in turn, growls and bites at her. I've told my little girl to just pet her when she's calm and sleepy...that's the best time to let them bond. They will eventually learn to play together...I just know to be patient...and let it happen in time.
I came extremely close to calling the breeder and asking to return my puppy before I asked you all for help. Please know that you are the reason I hung in there...and will continue to do that!!! You are such a wonderful support system!!! THANKS SO MUCH!!!