Talk to her former foster parents to find out what they've observed.
Look at
www.radzebra.org www.attachment.org
Has she actually been evaluated by a qualified attachment specialist? They should be able to give you an idea of how werious the issues are.
Attachment issues in a 13 year old are not something I would brush off as minor without some serious investigation. Where was she the first 3 years of life and how was her care? How many moves? What reasons were given for the moves?
These things all affect the level to which she may suffer from attachment problems.