Hi. Unfortunately you didn't present the text Lea is writing, which prevents me from seeing the opening sentence and the ending sentence. This makes it impossible for me to answer her question. However, I will try to help you as best I can.
To revise the final sentence of a text, adding a transition with the beginning of that text, you must cause a relationship between the beginning and ending sentences. This relationship can be achieved through words that show that the final sentence is a conclusion of the information presented in the initial sentence. For this, you can add, to the final sentence, words like "as a result," "therefore," "if so," "in this case," among others.