My impression from the text is Miss Watson is a resident of Meryton who received visits from militia officers when they first arrived.
Ever-watchful Mrs Phillips at Meryton noticed Colonel Forster & Captain Carter visited Miss Watson less.
Perhaps an older relation of Miss Watson's disapproved of the officers' visits and told them to come less often.
Or to speculate, Miss Watson found out Colonel Forster's affections were engaged elsewhere; So was less interested in the officers visits.
Mrs Phillips spotted Col. Forster and the Captain at Clarke's Library, perhaps feeling socially putout as they were still new in Meryton.
Lydia's interest in this snippet of news may've given Mrs Phillips ideas for officers' visits. ;-)