"All Ashkenazim probably have fanishingly small traces of Sephardi genes, so much so that it's part of the standard Ashkenazi reference DNA. So whilst you might be a bit Sephardi, it won't show up in a DNA test unless you're more Sephardi than the average." (source)

"If she's marrying a Sefardi, then she'll have to take on all the Sefardi customs." (Glinert)