We had to deal with some of what you are working through. My Dh grew up in foster care, so has had a unique understanding and perspective on foster care and adoption. Having said that, he also has had to revisit many difficult memories and experiences as we've gone through our foster parenting training and our adoption process.
You might look into taking the pre-certification classes for foster and adoptive parents in your area. This will give you some information as a family so that you have a more firm basis for making your decision, whatever that would turn out to be.
I would caution you that while adoption can be wonderful and the blessings abundant, it may not be quite what you and your daughter envision. Obviously children are not placed in foster care under happy circumstances and often have emotional issues that need to be worked through. This can take years...and years...of intensive therapy. Many children are socially delayed, sometimes several years below their chronological age, by the various traumas in their lives. While this doesn't sound so daunting in theory, living with a child who is chronologically 12 or 14 but who socially interacts on a 6 or 8 year old level (all while dressing and talking as a 12 or 14 year old) can be pretty tough at times. Additionally there are often brain processing differences due to early neglect and/or drug or alcohol exposure in utero. These brain differences are not visible on the outside, so the child appears 'normal' but has difficulty processing and responding to anything going into his/her brain. Because it is an invisible physically handicapping condition, exhibited only through behaviors, it can be pretty difficult to figure out and work with. Many, MANY people don't want to acknowledge the problem. Including professionals.
If you browse through the 'Special Needs Adoption' forum threads you can read about the various issues that many families are dealing with. Some are very, very sad and downright disheartening and depressing - and not because of lack of love or willingness to work through the problems with a child. Other situations are a testament to sheer endurance in the face unimaginable horrors. And there are still others who have various ups and downs, but they are not nearly as draining to the family's physical, mental, emotional and financial resources as the more severe cases.
I don't wish to discourage you, but do want you to do the research to find the best path for your family. Painful as it is you really should do some research on early childhood neglect and attachment disorders, particularly if you wish to adopt an older child. Here are a couple of web sites that can give you alot of information and provide some other netlinks to get you started.
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Welcome to Attachment & Trauma Network - ATN
Hope this helps.