[S]he has the ears of a ...?

Solution 1:

Bats are known for their impressive hearing, so that could be an option, while owls also have excellent hearing ability.

However, the animal with the best hearing is the Greater Wax Moth, which can hear sound frequencies of up to 300,000 Hz. In comparison, most humans can only hear up to 20,000 Hz.

However, I don't think

She has the ears of a greater wax moth

will work too well. May be best to stick with the owl.

Solution 2:

There's a famous quote of Gimli (LOTR):

I have the eyes of a hawk and the ears of a fox

Google returns about 500k results for "ears of a hawk" and 250k results for "ears of a fox" so it's quite popular, and should be quite well understood, because our 4-legged hairy friends, as well as their wild cousins, are known for their excellent hearing.

Solution 3:

I'm reminded of the old cartoon, Marshall BraveStarr;

"Eyes of the Hawk, Ears of the Wolf".

The premise being that the titular character had these qualities, including the "strength of the Bear", and "speed of the Puma".

He also had a robot horse and was a Wild West-era cowboy sheriff in space, so this might not be relevant.