मैं रोज़ सुबह नहाती हूँ।

Because the speaker is feminine singular.

In this kind of sentence, the main verb agrees with the subject’s gender and number:

• मैं ... नहाती हूँ = said by a woman/girl
• मैं ... नहाता हूँ = said by a man/boy

So -ती shows feminine singular here.

Hindi often shows the speaker’s gender through the verb form, not through मैं.

• मैं always means I
• The gender is revealed by:
  • नहाती = feminine
  • नहाता = masculine

So even though मैं is the same for everyone, the verb tells you whether the speaker is male or female.

हूँ is the first-person singular form of the verb to be in the present tense.

In a habitual sentence like this, Hindi commonly uses:

• a habitual verb form: नहाती
• plus the auxiliary हूँ

So:

• मैं नहाती हूँ = I bathe / I take a bath

For मैं, the auxiliary is हूँ regardless of gender:

• मैं नहाता हूँ
• मैं नहाती हूँ

It is a habitual present sentence, so it corresponds to English simple present:

• I bathe every morning
• I take a bath every morning

It does not mean I am bathing right now.

If you wanted present continuous, Hindi would normally use रहा / रही / रहे:

• मैं नहा रही हूँ = I am bathing

It combines two time expressions:

• रोज़ = every day / daily
• सुबह = morning / in the morning

Together, रोज़ सुबह means every morning.

So the sentence gives a habitual time:

• daily
• specifically in the morning

The dictionary form is नहाना, meaning to bathe / to take a bath.

Here is the pattern:

• dictionary form: नहाना
• habitual masculine singular: नहाता
• habitual feminine singular: नहाती

So नहाती हूँ is built from the verb नहाना.

Because Hindi often uses time words directly without a postposition.

So expressions like these are normal:

• सुबह = in the morning
• शाम = in the evening
• रात = at night
• आज = today

You do not need को here.
मैं रोज़ सुबह नहाती हूँ is completely natural.

Yes, Hindi word order is fairly flexible, especially with time expressions.

The most natural version here is:

• मैं रोज़ सुबह नहाती हूँ।

But other orders may also be possible depending on emphasis, for example:

• मैं सुबह रोज़ नहाती हूँ।
• रोज़ सुबह मैं नहाती हूँ।

Also, because the verb already shows the subject, Hindi often drops मैं if the context is clear:

• रोज़ सुबह नहाती हूँ।

That still means I bathe every morning, said by a female speaker.

Because हूँ is used with मैं.

Present forms of to be include:

• मैं ... हूँ = I am
• तुम ... हो = you are
• वह ... है = he/she/it is
• हम ... हैं = we are
• वे ... हैं = they are

So:

• मैं नहाती हूँ = correct
• मैं नहाती है = incorrect

Yes, very often.

Hindi frequently drops the subject pronoun when it is understood from context, especially in conversation.

So both are possible:

• मैं रोज़ सुबह नहाती हूँ।
• रोज़ सुबह नहाती हूँ।

The second version still sounds natural, and नहाती हूँ still tells you:

• the subject is I
• the speaker is female

Yes. You may see:

• रोज़
• रोज

Both are common in modern writing.
The version with the dot, रोज़, reflects the z sound more explicitly.

Learners should recognize both spellings as the same word in everyday use.