The following link :
http://www.yorkietalk.com/forums/gen...ml#post4449670
will bring you to the posting that has the research link.
New published data Feb 1 2014 on a cohort study of 2505 Viszlas does not show a strong co-relation between mammary tumours and either the age of spaying or intact/spayed females. Furthermore a systematic review of the literature Footnote (36) indicates only a weak co-relation in previous studies.
Authors Conclusion for this whole study is that more research is needed!
For the OP I how-ever agree with all the advice given. For many reasons as a novice pet owner, it would be best to spay your girl.