。
She makes a living as a teacher.
Literal
She [topic-は] teacher [object-を] doing livelihood [object-を] is-making-up.
Two collocations stack here. 教師をする/教師をしている is a casual way to say 'work as a teacher,' using a profession noun + を + する (literally 'do teacher'). Then 生計を立てる ('to make a living, support oneself') is the standard set phrase for earning a livelihood — literally 'to set up one's livelihood.' The means of the livelihood (teaching) is established by the first clause; 生計を立てている in resulting state captures her ongoing employment. Japanese also offers として ('as, in the capacity of') as an alternative role-marker — 教師として would emphasize the role itself rather than the activity of doing the work.