。
My sister's making huge strides, you know.
Literal
I [of-の] older-sister [subject-が] great-leap is [emphasis-よ].
大躍進 literally 'great leap forward' — historically associated with Mao's Great Leap Forward, but in casual modern usage means 'big breakthrough, making huge progress.' 姉 is the humble form for one's own older sister. A phrase of pride/excitement about a family member's success.