User can't see chatter group that she's a member of

I added a user to a chatter group but if she searches in Salesforce for the name of the group it's not found.  However, I gave her the URL to the group and when she goes to that URL she can see the group and post to it.  Why can't she see the group when she searches for it?

• The user's license is Salesforce.
• The group is set as Public