She's at least 2 and 1/2 foot tall.
Please clarify. Do you mean 2 1/2 feet long (as in she's that tall when standing on her hind legs)? Because I help measure dogs for agility trials and a 2 1/2 foot dog (30 inches) when measured at the shoulder is HUGE. Like getting into Irish Wolfhound/Great Dane territory! No coyote cross will be close to that height and even few pure bred GSD will be that tall.
Coyote crosses are much more rare than people think. Their breeding cycles don't sync well with domestic dogs, so unless your dog was created in a laboratory it is probably not one. Lots of people think they have coy-dogs, but in fact scientists have found almost all do not have any coyote DNA when tested.
I'm with dianerra, looks like a sable GSD. The breed varies widely in size depending on lines. You should see some of the GSD I see at agility trials; Border Collie size!