"had been preparing" implies that she had previously been preparing dinner, but had finished by the time you arrived home. It pushes the action further back into the past. You could say this, but it would be a bit strange. "was preparing" means she was actively preparing dinner when you arrived home. This is most likely what you mean.

In my opinion, both of them are right but the second one sounds more natural. The first one would sounds more natural if you write it as “she had been preparing dinner before I arrived home” because I think the word ‘when’ usually used when you want to describe two actions at the same time. Please correct me tho if I am the wrong one in here ^^

https://m.youtube.com/watch?v=ud2wlMNmhVE https://m.youtube.com/watch?v=odDSbWHUGYk

Hello. Can you with my englesh please

She was preparing dinner when I arrived home. -------- This is a PAST CONTINUOUS TENSE is formed by combining the past tense of to be (i.e., was/were) with the verb's present participle (-ing word). It is often used to describe conditions that existed in the past. The past continuous tense is used to describe actions that began in the past and often continued for a short period of time after the action started. This tense describes actions or events that happened at a specific time in the past. These actions are usually no longer happening at the time the sentence is being said or written. She had been preparing dinner when I arrived home ----------- This is a PAST PERFECT PROGRESSIVE TENSE indicates a continuous action that was completed at some point in the past. This tense is formed with the modal "HAD" plus "BEEN," plus the present participle of the verb (with an -ing ending): "I had been working in the garden all morning. Further explanation------ The past perfect continuous tense (also known as the past perfect progressive tense) shows that an action that started in the past continued up until another time in the past . The past perfect continuous tense is constructed using had been + the verb's present participle (root + -ing).