هي كانت قدام المراية وعم تغسل وجهها.

A natural breakdown is:

• هي = she
• كانت = was
• قدام = in front of
• المراية = the mirror
• و = and
• عم تغسل = washing / is washing
• وجهها = her face

So very literally, it is something like She was in front of the mirror and washing her face, while more natural English is She was in front of the mirror, washing her face.

Not always. In Levantine, subject pronouns are often dropped when the meaning is clear from the context or the verb.

So both of these can work:

• هي كانت قدام المراية وعم تغسل وجهها
• كانت قدام المراية وعم تغسل وجهها

Including هي can make the sentence clearer, more explicit, or slightly more emphatic: she was in front of the mirror.

Because this sentence is talking about a past situation.

In Levantine, for a sentence like she is in front of the mirror, you usually do not use a present-tense word for is:

• هي قدام المراية = She is in front of the mirror

But in the past, you do need كان / كانت:

• هي كانت قدام المراية = She was in front of the mirror

Since the subject is feminine singular (هي), the form is كانت.

قدام means in front of.

Here it is used spatially:

• قدام المراية = in front of the mirror

It is a very common Levantine preposition/adverb. You can use it with many places or objects:

• قدام البيت = in front of the house
• قدام الباب = in front of the door

Because this is Levantine Arabic, not Modern Standard Arabic.

In everyday speech, many words are different from MSA. المراية is a common Levantine word for the mirror. So this is just normal spoken vocabulary.

Also:

• الـ = the
• مراية = mirror

So المراية means the mirror.

عم + imperfect verb is a very common Levantine way to show an ongoing action, similar to English be + -ing.

So:

• عم تغسل = she is washing / she was washing, depending on context

Here, because the sentence is already set in the past by كانت, the meaning becomes was washing.

This is different from:

• غسلت = she washed (completed action)
• بتغسل = often she washes / she is washing depending on context, but less explicitly progressive than عم تغسل

So عم is what strongly gives the sense of an action in progress.

It could. In fact, كانت عم تغسل وجهها is also very natural and makes the past progressive especially clear.

But in this sentence, the past setting is already established by كانت in the first part:

• هي كانت قدام المراية وعم تغسل وجهها

So the was idea carries over into the second part. In English, this is similar to saying:

• She was in front of the mirror and washing her face
• more naturally: She was in front of the mirror, washing her face

If you want to be more explicit, you can say:

• هي كانت قدام المراية وكانت عم تغسل وجهها

That repeats كانت, but it is not required.

Literally, yes: و means and.

But in sentences like this, English often translates it more naturally as and, while, or even just with a comma:

• She was in front of the mirror and was washing her face
• She was in front of the mirror while washing her face
• She was in front of the mirror, washing her face

So the Arabic و is simple, but the best English translation may sound a little smoother than a literal and.

Because the subject is هي = she.

In the imperfect, Levantine uses different verb forms depending on the subject. Here:

• هو عم يغسل = he is washing
• هي عم تغسل = she is washing

So تغسل is the correct imperfect form for she.

Because Arabic attaches possessive pronouns directly to the noun.

Here:

• وجه = face
• ـها = her

So:

• وجهها = her face

This is very common in Arabic:

• وجهي = my face
• وجهك = your face
• وجهه = his face
• وجهها = her face

So instead of using a separate word for her, Arabic adds it as a suffix.

It describes one scene with simultaneous details.

The sentence gives:

• her location/state: she was in front of the mirror
• her ongoing action: she was washing her face

So the overall picture is one continuous moment: she was standing there, in front of the mirror, washing her face.

That is why the sentence feels very natural as a description of an ongoing scene in the past.