。
Her English has improved remarkably lately.
Literal
She [topic-は] recently English [subject-が] remarkably progressed.
A double-marking pattern: the topic 彼女は ('about her') sits alongside the subject 英語が ('it's English that') — telling you both whose progress and which skill area. The adverbial 素晴らしく ('remarkably, splendidly') is the く-form of the i-adjective 素晴らしい — it shifts a quality word into manner. 進歩する ('to progress, advance') is more neutral than 上達する ('improve in skill'), often used for both individuals (進歩する人) and abstract things (技術が進歩する 'technology advances'). The past tense 進歩した covers the recent stretch up to now.