Cô ấy đã lầm về ông ấy.

Vietnamese often uses kinship terms or social titles where English uses pronouns.

• cô ấy literally means something like that woman / that young woman
• ông ấy literally means that man / that gentleman / that older man

In natural translation, these often become simply:

• cô ấy → she
• ông ấy → he / him

So Vietnamese is not using a completely neutral pronoun system here. It is also showing how the speaker views the people socially.

Because ấy belongs to each noun phrase separately.

• cô ấy = she / that woman
• ông ấy = him / that man

It is not like English, where you would avoid repeating part of a pronoun system. In Vietnamese, each person reference is built on its own, so repeating ấy is completely normal.

Here, ấy helps turn cô and ông into third-person references.

đã marks the situation as past or completed.

So:

• Cô ấy lầm về ông ấy = She is/was wrong about him depending on context
• Cô ấy đã lầm về ông ấy = more clearly She was wrong about him

A useful way to think of đã is that it often places the event or state in the past, but it is not exactly the same as an English past-tense verb ending.

Yes.

Cô ấy lầm về ông ấy is possible. Vietnamese often leaves time reference to context.

Adding đã makes the past meaning more explicit. Without it, the sentence could mean:

• she is wrong about him
• she was wrong about him

depending on the surrounding context.

Here lầm means to be mistaken or to be wrong.

So the sentence means that her judgment or belief about him was incorrect.

This is slightly different from some related words:

• sai = wrong, incorrect
• nhầm = mistaken, confused, mixed up
• hiểu lầm = misunderstand

In this sentence, lầm focuses on being mistaken in one’s view or judgment.

It is understandable and correct, but it can sound a bit formal, literary, or old-fashioned depending on context.

In everyday Vietnamese, people might more often say things like:

• Cô ấy đã sai về ông ấy.
• Cô ấy đã hiểu lầm ông ấy. if the meaning is She misunderstood him

So lầm về is possible, but not always the most casual modern phrasing.

về means about / regarding here.

So:

• lầm về ông ấy = be mistaken about him

It shows the topic of the mistake.

This is important because it is different from saying she confused him with someone else. For example:

• Cô ấy nhầm ông ấy với người khác = She mistook him for someone else

But in your sentence, the idea is not confusion of identity. It is being wrong about him.

Vietnamese does not usually change pronouns the way English does.

English has:

• he for subject
• him for object

Vietnamese often uses the same form in both positions:

• ông ấy = he
• ông ấy = him

The role is understood from word order and sentence structure, not from a special case form.

The structure is:

Subject + past/aspect marker + predicate + topic/prepositional phrase

So here:

• Cô ấy = subject
• đã = past/completed marker
• lầm = predicate
• về ông ấy = prepositional phrase meaning about him

A very literal breakdown would be:

• Cô ấy — she
• đã — already / past
• lầm — be mistaken
• về ông ấy — about him

Yes, potentially.

Vietnamese pronoun choices often reflect age, respect, or social position.

• cô often refers to a woman younger than the speaker’s parents’ generation, or can be a respectful female form
• ông often refers to an older man or a man treated with respect

So the sentence may suggest that the man is older or socially respected. It is not as socially neutral as English she and him.

That said, exact nuance depends on context and the speaker.

Not exactly in the most direct way.

Cô ấy đã lầm về ông ấy is closer to:

• She was wrong about him
• She was mistaken about him

If you specifically want She misunderstood him, Vietnamese more naturally says:

• Cô ấy đã hiểu lầm ông ấy

So the given sentence is about a wrong judgment or belief, not necessarily a direct misunderstanding of his words or intentions.