Learn Hardcore Japanese: kanozyo ha maiasa yotei wo tetyou ni kakikonde iru. dakara wasuremono ga sukunai wake da. - She writes her schedule in her planner every morning. That is why she has few forgotten items.

彼女かのじょ　は　毎朝まいあさ　予定よてい　を　手帳てちょう　に　書かき込こんで　いる。　だから　忘わすれ物もの　が　少すくない　わけ　だ。kanojo wa maiasa yotei o techou ni kakikonde iru. dakara wasuremono ga sukunai wake da.

She writes her schedule in her planner every morning. That is why she has few forgotten items.

Breakdown of kanojo wa maiasa yotei o techou ni kakikonde iru. dakara wasuremono ga sukunai wake da.

はwa

topic particle

をo

direct object particle

Questions & Answers about kanojo wa maiasa yotei o techou ni kakikonde iru. dakara wasuremono ga sukunai wake da.

Why is は used after 彼女?

は marks 彼女 as the topic of the sentence.

So 彼女は means something like as for her or she in the sense of speaking about her.

This is very common in Japanese:

彼女は毎朝予定を書き込んでいる。 = As for her, she writes her plans down every morning.

If you used が instead, it would sound more like you are specifically identifying her as the person doing it, rather than simply introducing her as the topic.

What exactly does 毎朝 mean, and where does it fit in the sentence?

毎朝 means every morning.

It is a time expression, and time expressions in Japanese are often placed near the beginning of the sentence, before the main action:

彼女は毎朝予定を書き込んでいる。

That word order is very natural.

You could think of the sentence as:

As for her, every morning, she writes her plans into her planner.

Japanese word order is flexible, but placing 毎朝 before the object and verb is very standard.

Why is it 予定を but 手帳に?