She was 19 when Lucas first proposed in 5x05 and that was 1 বছর after graduation. Jump অগ্রবর্তী the 4 আরো years to the beginning of season 5 and she would be 23. And since a decent amount of time is supposed to have taken place from S5-now, It's a নিরাপদ venture to say she's around 24 =]