Re: Dexter Season 7 (spoilers)
I think that if this was the fourth, fifth, or even sixth season then you would probably be right about LaGuerta being somehow steered away from pursuing this case, but seeing as this is probably the penultimate season, she will probably be the one to find out about Dexter outside of obviously Deb. Plus, she's seems fully convinced that Doakes wasn't the Bay Harbor Butcher, and she also seems nearly convinced that Dexter might just be the BHB.
And while it would be out of character for Deb to kill Laguerta, it's been established that she not only loves Dexter, but she's fine with him doing what he's doing. I think that if she realizes that LaGuerta is close to bringing Dexter down, she will do something about it.