Complex sentence: Dickinson's mentor Malbone was one of the leading miniaturists at that time, and much of Dickinson's early work reflects the style of that portrait, including delicate modeling and soft color.
Split into simpler sentences: Dickinson's mentor Malbone was one of the leading miniaturists at that time. Much of Dickinson's early work reflects Malbone's style as exemplified by the portrait he made of Dickinson, including delicate modeling and soft color.