Need legal advice.?

Who's your publisher? Just curious. And, no, if you've contracted with someone to publish this book, you can't shop around another version of it.

You can't have two versions of the same book out that'd definitely breech your contract. How can you not know that if you're a legitimately published author? And just because you use long paragraphs and complex sentences doesn't make a novel "adult". It might just make your writing sound pretentious if that's all you ever do, as if you're writing to say THIS IS A BOOK FOR ADULTS. Readers don't want to read something that reads as if the author was trying to prove they're intelligent. It gets stuffy, it gets monotone if you don't really vary your diction and syntax.

When the book is dumbed down it will have very different words, therefor I'm going wit her (my publisher) because she was the only game in town so to speak when I did my first book so sentimental reasons. Won't it be same story, different book the more adult version? A plan b is to have a friend send it to an agent etc. I believe I still hold the copyright to both.

Since you obviously don't want to dumb down your writing, don't. If your publisher won't publish it in it's original form some other probably will since you've already had one book published. If you were painting would your agent tell you what colors to use? I don't think so.. I guess you'll just have to stand up to your publisher and let him/her know you won't be dictated to.

Not if you accept the publisher's offer. It wouldn't hurt you to have an agent for exactly these sorts of negotiations.

Well, this is an example of adjusting to fet the needs. If your publisher says this, I recommend listening to him - especially since he is the one who will decide if your book is printed or not.