I'm pretty sure it was actually Edie, as I agree they were running out of storyline for her - and that they have too much storyline ready to go for both Gaby and Lynette's mom. I think she realized that she'd always be alone because no one would truly accept her for her, and she couldn't take it. I don't think it was so much that Carlos dumped her as much it was the realization that she was going to grow old alone like her mom apparently did. Even her own son didn't really need her.
I think that Gaby will cheat on Victor with Carlos and that will lead to Victor sending out his goons. Or she'll sabotage his campaign. Either way, that actually could be an interesting storyline - lots of fiery/strong personalities.
I think Lynette and her mom will end up making peace with each other by the end of next season, as her mom tries to be a real mom for once and help her through the battle.
And yes, I'm sure Danielle will blow Bree's and Orson's neatly arranged plan. It really is hard to like her character - what a brat!