I totally agree with what Carrie said (yogachick
having a second baby is hard-- it is a transition for everyone-- but you will all get through this okay, but please try to involved your husband so he knows you need him more, DD1 needs one on one time with him-- and make sure you keep him posted if your symptoms change and/or get worse.
can you ask a close friend to bring a special gift for DD1 and come over and not fuss over the baby, then take DD1 out for something really nice? The zoo, some ice cream, shopping at a toy store to pick out a new toy for her and also one for her sister?
lastly, i noticed my DS1 was having some issues (can't remember how many days/weeks postpartum) and I sat him down (he is 3.5 years) and looked him straight in the face and held him and told him "you know how much i love you, right? you know mama will ALWAYS be here for you, right?" then I explained what the baby needs and how I did those SAME things for DS1 when he was a baby. Then I asked him if he wanted to do something special just him and mama (we do this more frequently now that DS2 is 7 mos) tomorrow. We talked about what we could do together, and eventhough he is only 3.5 he nodded the whole time with tears streaming down his face and I could tell he understood what I was talking about.
since your DD1 is 7 years old, she will be able to be much more involved and understanding, I would think, if you just sat her down and explained it.
I know it's hard-- this too shall pass.
bottom line: don't rule out PPD.....but do give it a few more days, a visit with your therapist, some more self care (naps, baths, foot massage) and forgiveness etc...update us will you?