A lot of short haired dogs need to be deshed quite often to keep it to a minimum.
There were several short haired dogs that would come into the grooming shop I worked at. The first couple of times they had large amounts of dead hair (which is what comes out when you deshed a dog. It's the dead undercoat.). The dogs that came in on a regular basis, every 3-4 weeks, didn't have much dead coat after about 4 visit.
If you just deshed a little (or even what you might think is a lot) every now and then it's just going to keep building up. The dogs that would come in with a lot of dead coat; we'd spend 45-60 minutes desheding at a VERY high pase. Porbably getting out 2-3 times as much hair as you would normaly get out. So if you add that up it's like 3-4 hours of desheding every month for a regular basis. Once you get the majority of the coat out then it's just basi upkeep.
However you need the right tools and need to know the right way to use them (It makes a world of difference). A furminater, if she's shedding that much, wont work. Depending on her coat type, you'll need coat strippers of different sizes, shedding blades, and deshedding combs, you also might need the rubber deshedding scrubbers.
It all depends on her coat. You could try taking her into a Grooming salon so that they can get the majority of the coat out this time and then you can do the basic upkeep. Or even take her while she's getting rid of this winter coat. If she never got rid of her winter coat, I wouldn't be surprised if that's what's going on now.