In which situation, we normally say the follow, 好好养病，不久你就会好的。 好好静养，我平时会来看你的。 少运动，多休息。 伤筋动骨一百天，好好养病。 祝你早日康复。 There are some good alternatives you might say in this situation, (at least they're what i expect to hear from those who come to see me, haha) 需要钱的话就说话。 有空我就来照顾你。 想吃啥告诉我，我给你弄去。

If she's a very close friend of mine, I might joke about it in a friendly way, hehe. 祝你早日康复 is a bit too formal, but it's a very safe way to express your good wish to a person who has broken his leg.

谁干的，我找他算账去~

若他是你極親密，可以開玩笑，又懂典故的朋友 : 大難不死，必有後福。 不用引錐刺股，你終於有時間好好讀書了。 可惜妳斷的不是胳臂， 不然妳就成良醫了。

祝你早日康复。I think this is enough.