She is thinking about taking a couple of courses at a cooking school.
Literal
She [topic-は] cooking school [at-で] two-three [possessive-の] courses [object-を] take-shall [quotative-か] [quotative-と] is-thinking.
~ろうかと考えている combines the volitional ~おう/~よう with か ('shall I?') and と考えている ('is thinking'), expressing ongoing deliberation. 料理学校 is a compound noun for 'cooking school.' ２、３の is a natural way to say 'a couple of, two or three.'