verb

think deeply about something that makes one unhappy, angry, or worried.

she had brooded over the subject a thousand times

worry about,fret about,agonize over,mope over,moon over,languish over,feel despondent about,grieve over,sulk about,eat one’s heart out over,think about,ponder,contemplate,pore over,meditate on,muse on,mull over,dwell on,ruminate on/over,chew over,puzzle over,weigh up,turn over in one’s mind