The Dexter facebook page keeps posting all these teaser videos, talking about Deb's struggle. They always mention that she had to choose between killing her brother or LaGuerta. Every time I'm like nope, she totally didn't have to kill either. If she wanted Dex to live all she had to do was leave and let him kill LaGuerta himself. Sure that's effectively killing LaGuerta, but the moral implications are not nearly as severe.
The entire season is going to be based around a ridiculous scenario constructed as a plot device. Just like last season was based around Deb having an unethical therapist that decides to suggest her patient is in love with her own brother, which causes Deb to go to the church and discover him killing someone. That one wasn't so bad because there are lots of ways for her to find out; they just chose a stupid one. However, there aren't lots of ways to make Deb choose between killing her brother or an innocent. The whole show is pretty retarded at this point