Well, no one mentioned the type of food they are feeding. Are you using a premium dog food? Eukanuba or Iams would be good. Does she have any skin problems? Premium food helps with those, too. I am not pitching Iams products, but they do have the extra amino acids that should help the skin and coat. However, this is a phenomenon more particularly for the indoor/outdoor dog. Because they do not need to retain the coat for winter, they lose it all year around. I'm assuming you have a double coat here, considering the breeds in her mix. A very popular grooming tool at my house is one that I did first see in the horse world. it looks like a rubber brush with GIANT teeth. I think Booda first put them out. They get down into the coat but are unlikely to break hair off as the teeth are about the diameter of a pencil. All my animals line up for grooming (cats included) and we have less of the shed hair around when I use it regularly.
Good Luck.