。
She makes a living selling her paintings.
Literal
She [topic-は] her own paintings [object-を] sell [then/by-て] livelihood [object-を] is-establishing.
生計を立てる is the set phrase for 'to make a living' — literally 'to set up one's livelihood.' The te-form 売って ('selling') connects the means to the predicate: she earns her living *by* selling her paintings. With ~ている, 立てている describes an ongoing way of life rather than a one-time event. 絵 here covers paintings, drawings, and other visual artworks; in artist contexts it leans toward 'painting.'