Basically, the research "jury" is still out on DCC. There seem to be some benefits, particularly in premature infants, but there is just not enough research out there for OBs, the ACOG etc to recommend it as standard protocol for all births. Here are some research studies that are newer that you could show her:
http://www.ncbi.nlm.nih.gov/pubmed/22673168 (this is a meta-analysis and appears very good)
http://www.ncbi.nlm.nih.gov/pubmed/22089242 (this looks at long-term outcomes)
Here is the ACOG's most recent statement on DCC: http://www.acog.org/About_ACOG/News_Room/News_Releases/2012/Time_to_Clamp_the_Cord
Personally, I don't think DCC is going to be my hill to die on. However, if you are already concerned about her, I would switch. If you liked her otherwise, it would be different.