In this sentence, which answer is correct?

1. She has a boyfriend who she loves.
2. She has a boyfriend whom she loves.

Or should there be a comma?
And what are the rules for who/whom?
Thanks in advance.
The object case of who, whom, is disappearing, as many old inflections in English have done over the past few hundred years.

It is still always used in a prepositional phrase:
She has a boyfriend with whom she lives.

Except if the preposition is at the end of the clause:
She has a boyfriend who she lives with.
Who did he give the ring to? (informal)
To whom did he give the ring? (very formal)
Whom is grammatical, however I think modern day grammarians accept even who here.
Somehow the sentence sounds a little odd to me.
I would say "She has a boy friend and she loves him."
Students: We have free audio pronunciation exercises.
 AlpheccaStars's reply was promoted to an answer.
Rainbowwalkershould there be a comma?
Here's the contrast between using a comma and not using a comma.

She has a boyfriend who she loves. (And she has several other boyfriends who she does not love).
She has a boyfriend, who she loves. (She has a boyfriend, and she loves him.)