"... isn't there a massive chance of one of her lab members getting scooped to a paper because they aired unpublished results to the world?"This is the big fear that seems to stop researchers from even considering blogging about their work. But for most labs the risk is not very high, and there are benefits for everyone.
Benefits first. I'm a bit of an idealist about science - I think cooperation is more powerful than competition. NIH thinks so too - If you call them with a new research idea, they don't warn you to keep it under your hat because others are working on similar stuff. Rather they try to put you in touch with these people to encourage collaboration. Blogging about our ongoing research doesn't only actively promote interaction with other researchers, it helps me remember that science should be a community activity.
I also think the risks are overestimated. Although one dramatic scientific stereotype is of research groups competing for glory, in reality very few of us are engaged in fierce competition with groups trying to use the same methods to answer the same questions. If you are in such a competition, blogging about your research might not be a good idea. On the other hand, thinking about blogging might cause you to consider ways to could reduce the competition and promote collaboration instead.