Firstly it isn't too late to relactate.
Secondly if at ALL possible get her off of soy formula, there are many many concerns about soy formula from the phytoestrogens, to the high levels of aluminum. Many governments from Israel to France have very strongly warned against the use of soy formula and the amount of soy in children's diets as they grow as well.
Adoptive Breastfeeding & Relactation
http://www.kellymom.com/bf/adopt/index.html
SOY FORMULAS
http://www.askdrsears.com/html/0/T000100.asp#T031004
When It Has to be Formula: Optimizing the Health of Your Formula-Fed Baby
http://www.naturalfamilyonline.com/go/index.php/226/optimize-health-formula-fed-baby/
Soy: Who Needs It?
http://www.todaysparent.com/baby/breastfeeding/article.jsp?content=20030807_101250_216#soywho
Known Contaminants Found in Infant Formula
http://findarticles.com/p/articles/mi_m0838/is_2000_May-June/ai_62141685
Phytoestrogens in soy-based infant foods: concentrations, daily intake, and possible biological effects.
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=9492332&dopt=AbstractPlus
Soy and Children's Health: A Formula for Trouble?
http://www.ehponline.org/docs/2002/110-6/niehsnews.html
Artificial baby milks:
how safe is soya?
http://www.babymilkaction.org/resources/briefings/tessasoya03.html
Paediatric Group Position Statement on the use of
Soya Protein for Infants
http://www.bda.uk.com/Downloads/soystatement.pdf#search=%27soya%20infant%20formula
Soy formula may inhibit intestinal development in babies
http://nutraingredients.com/news/news-ng.asp?n=56963-soy-formula-may