Nala08,
I found an adoptive family for my son about 6 years before I had my daughter. I knew I wasn't ready to be a parent when I found out I was pregnant with my son. I wasn't sure when I had my daughter, but I was in a much better position finacially and emotionally, plus, her father and I were still together and he wanted to be a part of her life (we are still together and she just turned one). I don't regret finding parents for my son who would be able to give him the love and support I just didn't think I would be able to give him when he was born.
Not raising my son myself didn't change the way I feel about my daughter. I love her with all my heart. But I still stand by my choice with adoption for my son. We did an open adoption so I get updates periodically and when he is older, I am okay with him knowing about me and possibly meeting me, but I know I wasn't able to provide for him when he was born.
Your daughter may have some rough times when she second guess her current parenting abilities, so you need to make sure you support her and give her the unconditional love that a child needs and she should be just fine. I know I am. :)