English - Word choice problem

你說到對，at last其中一個意思就是in the end.
但at last也有其他的意思，其中一個是：after much delay, effort, etc.中文作：終於（可參考牛津第六版）

你的句子：是Frankie終於得到那份工作（有用了很多努力之後的意思）

所以，用last會貼切得多，

希望幫到你朋友！

please tell me which one is correct and why dog choose

"at last" is used when you have done something as a procedure. It is the last procedure.
"at last" = 一連串步驟後的結果．
"in the end" is used when you are talking about the end of a story.
"in the end" = "結局" "通常係故事最後結局"

Therefore, you should use "at last" for the end of a procedure.