I'm definitely an amateur, so I apologize if this is the wrong spot.

The quote you are referring to isn't exactly talking about women running off with marauding Northmen--more that they were considered extremely attractive.

It is reported in the chronicle attributed to John of Wallingford that the Danes, thanks to their habit of combing their hair every day, of bathing every Saturday and regularly changing their clothes, were able to undermine the virtue of married women and even seduce the daughters of nobles to be their mistresses.

Keep in mind, a weekly bath and change of clothing was considered excessive by the typical Christian European. Additionally, Northmen were fond of bleaching their hair with lye soap and carried combs, ear spoons (for removing wax), tweezers, and such with them constantly.

The Northmen were also quite fond of clothing and tended to "peacock" a bit. Bright colors were a sign of wealth and success, and red (madder), blue (woad), and yellow (...lots of different things) were very common. Silk trim on tunics was considered a sign of wealth, as was tablet-woven trim.

There's also the whole filing lines in their teeth and painting them with red enamel, but that doesn't really come up often and I don't think it would make them particularly attractive.

Basically, let's assume you're an average bored noblewoman in, oh, what would one day be York. Along come these guys who take over the place. They're a bit bigger (not by much) than the locals. They're blonde. They don't smell as bad. They're dressed all fancy-like. It's easy to see where the local guys might feel a little inadequate.

Source: http://www.vikinganswerlady.com/hairstyl.shtml

(Please note: her site is generally pretty good for any Viking-related question.)