In a way that is full of charm; in an attractive, delightful, and enchanting manner.
Charmful + -ly. Adverbial suffix applied to the adjective to create an adverb form, though this construction is quite rare.
This is a 'double formation'—charm becomes charmful (full of charm) which becomes charmfully, showing how English builds word families by stacking suffixes like LEGO bricks!
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