adverbs and adjectives

I was teaching adj. and adv. and how we form the adv. from the adj. Also, that the adj. tells us something about the noun and the adv. about the verb.
Later on in the class, and not related to the above, the student had to make a sentence with: Sally/felt/really happy/to be / winner. So the student said Sally felt really happily to be the winner.
I corrected her to happy, and she said why? She felt happily tells us something about the verb felt.
Can you explain this to me so that I can pass it on to her?

I was teaching adj. and adv. and how we form the adv. from the adj. Also, that the adj. tells us something about the noun and the adv. about the verb.
Later on in the class, and not related to the above, the student had to make a sentence with: Sally/felt/really happy/to be / winner. So the student said Sally felt really happily to be the winner.
I corrected her to happy, and she said why? She felt happily tells us something about the verb felt.
Can you explain this to me so that I can pass it on to her?

The adjective ‘happy’ does not tell something about the verb ‘felt’; it modifies or tells something about the subject ‘Sally’. ‘Felt’ is a stative (as opposed to dynamic or action) verb. Its meaning is very similar to ‘was’. Sally felt (~ was) really happy (*happily) to be the winner.