the Dashwoods are out of deepest mourning. They stayed at Norland for six months after Mr. Dashwood died, did they not? The mourning traditions were not quite as strict during the Regency as they were during later times, so they probably would not have to wear black for a whole year, but may very well have for six months.

Mrs. Dashwood probably wouldn't have been out attending formal balls and such, but that doesn't really come into play for her at Barton. She might have avoided those if she were still in deep mourning.