मेरी दोस्त की बारी है।

Because मेरा / मेरी / मेरे changes to match the noun that follows it.

Here, दोस्त refers to a female friend, so Hindi uses मेरी.

A useful contrast:

• मेरी दोस्त = my female friend
• मेरा दोस्त = my male friend (when there is no following postposition)
• मेरे दोस्त की... = of my male friend / my male friend’s...

So in this sentence, मेरी tells you the friend is female.

No. It tells us about the friend, not the speaker.

In Hindi, possessive words like मेरा / मेरी / मेरे agree with the thing or person possessed, not with the owner.

So both a man and a woman can say:

• मेरी दोस्त की बारी है। = It’s my female friend’s turn.

दोस्त is a little flexible in real usage. It can refer to either a male or female friend, and the surrounding words often show which one is meant.

In this sentence, मेरी makes it clear that दोस्त means a female friend.

If you want to be more explicitly feminine, Hindi also has:

• सहेली = female friend

So:

• मेरी दोस्त = my female friend
• मेरी सहेली = my female friend

Both can work, though दोस्त is very common in everyday speech.

की is a possessive marker, similar to English ’s or of.

So:

• दोस्त की बारी = the friend’s turn

More literally, the structure is:

• मेरी दोस्त = my female friend
• की = ’s / of
• बारी = turn
• है = is

So the sentence is literally something like My female friend’s turn is.

Because का / की / के changes to match the noun that comes after it — the thing being possessed.

Here the possessed noun is बारी, and बारी is feminine singular, so Hindi uses की.

Compare:

• मेरे दोस्त का घर = my friend’s house (घर is masculine singular)
• मेरे दोस्त की बारी = my friend’s turn (बारी is feminine singular)
• मेरे दोस्त के दोस्त = my friend’s friends (दोस्त here is plural/appropriate के form)

So की is chosen because of बारी.

In Hindi, nouns before postpositions like का / की / के go into the oblique case. But not all nouns visibly change form.

दोस्त ends in a consonant, and nouns like that often look the same in direct and oblique forms.

So:

• direct: दोस्त
• oblique: दोस्त (same form)

That is why you do not see a visible change in दोस्त itself.

You do, however, often see the change in words around it. For example:

• मेरा दोस्त = my male friend
• मेरे दोस्त की बारी = my male friend’s turn

Here मेरा changes to मेरे because the masculine singular noun is now in the oblique environment.

बारी usually means turn, chance, or one’s go.

It is used in situations like:

• taking turns in a game
• speaking one by one
• standing in a queue
• waiting for a chance or opportunity

So मेरी दोस्त की बारी है। means that now it is the friend’s turn to do whatever the context is about.

Because Hindi normally puts the verb at the end of the sentence.

So the structure is very natural for Hindi:

• मेरी दोस्त की बारी = my friend’s turn
• है = is

English says:

• It is my friend’s turn

Hindi more literally says:

• My friend’s turn is

This verb-at-the-end pattern is extremely common in Hindi.

You would usually say:

मेरे दोस्त की बारी है।

Why मेरे? Because with a masculine singular noun like दोस्त, when it is followed by a postposition structure like की बारी, the possessive form becomes मेरे.

So the contrast is:

• मेरी दोस्त की बारी है। = It’s my female friend’s turn.
• मेरे दोस्त की बारी है। = It’s my male friend’s turn.

Yes. You can say:

मेरी सहेली की बारी है।

That also means It’s my female friend’s turn.

The difference is mainly nuance:

• दोस्त = friend, very common, casual, widely used
• सहेली = specifically female friend, a bit more explicitly feminine

So both are correct; दोस्त is just more general and very common in modern speech.