It's her key. Once I accept that the car came with more luxuries---such as keyless entry---than I really wanted, I'm quite happy with the design of the key. The folding "blade" keeps the overall length in check and prevents holes from developing in my pockets. The total volume would be awkward if I carried it on my key ring, but since I carry my car keys separately* from my house keys, work keys, and multi-tool, the size is not a problem.
* I do this for two reasons: (a) Since I have two cars---three in the short term---it seems foolish to carry all their keys all the time. (b) I like to minimize the amount of material dangling from the ignition, because it bothers me to have keys brushing my right knee, and I suspect it's damaging to the ignition switch to hang a lot of mass from it.