Do I necessarily need to insert the possessive pronoun "her" in the following sentence or can I just skip it?

Karen, a person, does X together with (her) friend Juliette.

I see that it's uncommon, but under specific circumstances (I thought maybe the back of a novel? => some kind of summary) this would sound right to me.

I suppose the word "friend" acts as the person's title here; for I'm pretty sure that it's okay to say:

She left the room with Doctor Jake.

And don't need to say "a doctor" / "her doctor".

So the real question should be can the word "friend" act as such a title and can other words (or only job titles (plumber) or maybe only offical titles (professor)?

Do I necessarily need to insert the possessive pronoun her in the following sentence or can I just skip it?

Karen, a person, does X together with (her) friend Juliette.

I see that it's uncommon, but under specific circumstances (the back of a novel, or some kind of summary) this would sound right to me.

I suppose friend acts as the person's title here; for I'm pretty sure that it's okay to say She left the room with Doctor Jake.

I don't need to say a doctor / her doctor.

Can friend act as such a title?
Can other words, such as job titles (plumber), act as titles?