Is it my fault she goes crazy? (long rant)

My dog Lucy is just over 2 years old and she's probably the happiest dog I've ever seen. My next door neighbor says Lucy enjoys life to the fullest. We spend alot of time together playing, training, and just hanging out. I've always tried to be calm and assertive with her. When we're alone, her behaivor is great. When we're around other people and dogs or people come over the house she acts like she was raised in the wilderness and is starving for human contact. She runs in circles all over the place. She whines. She starts to pant heavily. She jumps up and down. She pretty much goes crazy with excitement. People that know her will wait till she calms down before acknowledging her. People that don't know just freak out. Why does she continue to do this when 99% of the time she doesn't get any attention? A good example is this: our back yard is fenced and my wife has flowers planted all along the perimeter. Lucy knows she's not allowed in the "garden". When she sees our next door neighbor is out in her yard, she runs over stands in the flowers paws up on the fence waiting for her to come over which she won't because she knows Lucy's not supposed to be in the flowers. I just don't get it. We've done all the training stuff. Keeping her on a leash. Having her lie down. Putting her in her crate. Sometimes she gets so excited, she goes in her crate on her own. Everything only lasts a little while. She sneaks out of her crate. She starts crawing on her belly, thinking no one can see her. She just waits and BOOM she's gone again.
Is it possible I've caused this by not acting happy and crazy around her and using a high pitched voice when talking to her? Is she yearning for the kind of attention she doesn't get from me? The part I don't get is she doesn't get the attention from the people she's acting crazy around either. I'm the only one that plays with her. Do I need to get more excited when we play?
Lucy really is a good dog. She does listen when told to get off, lie down, go to her crate and stop. But why does she do it in the first place? I don't know if I can make it another year or two till she "matures".
Thanks for letting me vent. I know there are dogs that have much more serious problems than this. I'm very grateful Lucy is such a happy friendly dog. If this is the only problem I have, maybe I souldn't be complaining but when she acts like this it looks like she's not a well behaved dog and that bothers me.