امي كانت زعلانة، بس انبسطت لما اجت صديقتها.

It’s Levantine colloquial Arabic, not formal MSA.

A more natural Levantine-style spelling would often be:

إمّي كانت زعلانة، بس انبسطت لمّا إجت صديقتها.

Some clues that it’s dialect:

• بس for but
• انبسطت for became happy / was pleased
• إجت / اجت for she came

In MSA, the sentence would be phrased differently, for example:

• كانت أمي منزعجة، لكنها فرحت عندما جاءت صديقتها.

A helpful pronunciation is:

immi kaanet za‘laane, bas inbasatet lamma ijet sadi’ta

A more natural Levantine pronunciation might sound like:

immi kānet za‘lāne, bas inbasaṭat lamma ijet ṣadī’ta

A few notes:

• امي is usually pronounced immi in Levantine.
• زعلانة sounds like za‘laane.
• اجت / إجت is typically ijet.
• صديقتها is roughly sadi’ta or ṣadī’ta-ha, depending on how clearly someone pronounces the ending.

كانت is the feminine singular past of كان (to be).

Because the subject is my mother, which is feminine, Arabic uses:

• كان for masculine
• كانت for feminine

So:

• أبوي كان زعلان = My father was upset
• أمي كانت زعلانة = My mother was upset

In this sentence, كانت means was.

Because it agrees with the feminine subject, my mother.

In Levantine:

• زعلان = upset, sad, annoyed, for a masculine subject
• زعلانة = upset, sad, annoyed, for a feminine subject

So:

• هو زعلان = He’s upset
• هي زعلانة = She’s upset

Since أمي is feminine, the adjective must also be feminine:

• أمي كانت زعلانة

It most often means upset, sad, annoyed, or bothered, depending on context.

It does not always mean strongly angry. In everyday Levantine, زعلان / زعلانة can cover a range like:

• sad
• upset
• offended
• annoyed

So in this sentence, the mother was probably feeling down or upset, and then she became happy when her friend arrived.

Here بس means but.

In Levantine, بس is extremely common in speech for:

• but
• sometimes just / only, depending on context

In this sentence:

• أمي كانت زعلانة، بس انبسطت...
• My mother was upset, but she became happy...

So here it clearly means but, not only.

انبسطت means she became happy, she was pleased, or she cheered up.

The base verb is انبسط in colloquial Arabic, which often means:

• to enjoy oneself
• to be pleased
• to become happy

In this sentence, it refers to the mother, so the form is feminine past:

• انبسط = he became happy / he enjoyed himself
• انبسطت = she became happy / she enjoyed herself

So بس انبسطت means:

• but then she was pleased
• but she cheered up
• but she became happy

Because Arabic verbs already include the subject.

In English, you need:

• she became happy

In Arabic, انبسطت already tells you:

• past tense
• singular
• feminine

So the she is built into the verb.

If you wanted, you could add هي for emphasis:

• هي انبسطت But normally it is unnecessary.

لما here means when.

It introduces the event that caused the change in mood:

• انبسطت لما اجت صديقتها
• She became happy when her friend came

In Levantine, لما is very common for when in past-time contexts.

You’ll hear it in sentences like:

• لما وصلنا، بلشنا ناكل = When we arrived, we started eating
• لما شافها، ضحك = When he saw her, he laughed

Because اجت / إجت is the Levantine colloquial form of she came.

In MSA:

• جاءت = she came

In Levantine:

• إجا = he came
• إجت = she came

So this sentence uses the everyday spoken form.

Also, informal spelling often varies:

• اجت
• إجت

Both are commonly understood in casual writing.

صديقتها breaks down as:

• صديقة = female friend
• -ها = her

So:

• صديقتها = her friend

Because the friend is female, the noun is صديقة rather than صديق.

The full meaning here is:

• her female friend

So the structure is:

• صديقة + ها
• friend + her

Because Arabic often marks possession with a suffix attached directly to the noun.

Examples:

• أمي = my mother
• صديقتها = her friend
• بيتي = my house
• كتابك = your book
• سيارتهم = their car

So instead of saying something like friend of her, Arabic usually attaches the possessive ending directly to the noun.

Because casual Arabic writing usually leaves out short vowels, and dialect spelling is not fully standardized.

So all of these may appear:

• امي
• أمي
• إمي
• إمّي

In Levantine pronunciation, it is usually immi.

The same thing happens with other words in the sentence:

• اجت may also be written إجت
• لما may also appear as لمّا

So don’t expect one perfectly fixed spelling in informal dialect writing.

The sentence is built in two parts:

1. أمي كانت زعلانة

   • My mother was upset

2. بس انبسطت لما اجت صديقتها

   • but she became happy when her friend came

This is very natural Arabic word order. The subject أمي is stated once, and then the next verb انبسطت continues referring to the same person without repeating she.

So the flow is:

• subject introduced
• description of her state
• contrast with بس
• new verb showing her reaction
• time clause with لما

Yes. Since أمي is feminine, the words referring to her are also feminine.

In this sentence:

• كانت = feminine
• زعلانة = feminine
• انبسطت = feminine

And in the time clause:

• اجت is also feminine, but this time it matches صديقتها because her friend is female.

So Arabic agreement is doing a lot of work here:

• the mother is feminine
• the friend is feminine
• the forms show that clearly

This is one reason Arabic can often leave out separate pronouns.