Don't get the badge/notification for all my chats

There are 20 people in my organization - I have one-on-one chat threads with everyone, plus a whole bunch of topic-based group threads.  When I look at my sidebar/dashboard, I see the little red circle in every chat with individuals and groups except for one person - I think she's ignoring me but when I click on her name to see the chat, she has replied but I didn't get the notification. I can't find a setting that would control that. Advice? Could it be a setting on her end?