Has she always been this way? She is just trying to stay close to you, as she was in the womb. Babies that age do not really need to be left alone. Try wearing her or sitting on the floor and playing with her. I bet this is hard with an older child, unless that child is in school during the days. Or get big sis involved in playing baby games when you need to do something.
I had a high needs baby too. He would not let me put him down for almost a year unless I was right there with him, especially to sleep. I could not put him down (even after falling asleep at the breast) for more than 10 miutes or he would wake up crying. Around 7 mos he finally slept for 30 mins on his own! But we continued to cosleep and he is happy. I just slept with him or read a book, wached TV, or talked on the phone while he slept on me.
He became very active around 4-5 mos when he started crawling (scooting backwards), and was walking by 9 mos, so there is a weird dichotomy of dependence and independence going on. My son is 2.5 now and still enjoys a lot of attention but not nearly the way he did as a baby.
I believe that forming an early bond with your child will only make them more independent individuals as they grow up, and I can see this in my 2.5yo. You cannot spoil a baby. Just help them feel secure as a person and member of the family. With love and respect they can feel confident in their place in the world.
It does get easier, but just realize that she is expressing a need in the only way she knows how, by crying. Put yourself in her shoes and think about what life is like for her. And enjoy this baby stage as it goes by so fast. (You know, you have a 5yo!)
Read "The Baby Book" by Dr. Sears. It may help explain it better than I can. I don't think a baby needs to be "broken."