If you are fully aware of this and can make her extend her claws by pressing on the underside of her toes, and you can tell she genuinely doesn't have claws on
that foot, does she for some reason have claws on
all her other feet?
If both front feet have no claws that extend when you push under her toes, it's possible that sometime in her past she was declawed. But no vet would ever do that only to one foot.