Adverb
In a smiling manner.
Source: Webster's dictionarythe girl reminded her smilingly of their childhood spent together Source: Internet
All the familiar faces of the corporate world on Page 3 were peering out of newspaper columns and smilingly telling citizens like me how much there was to praise in such foresight. Source: Internet
When I protested, she smilingly opted for the “how do you do” followed by a handshake. Source: Internet