Talking to her will probably not help much. Maybe asking questions. Questions fire thinking. Be careful that your questions are free of preconceptions. Be emphatic. It is not always necessary to see a professional, but be aware for signals that you can't handle.

Tell her that nothing is ever as bad as it seems - but, sadly, never as good as it seems either.

Just let her know you are there for her if she needs it.

can you narrow it down a bit as it leaves too many possibilities as it is?

Awe I'm very sorry about your friend that she's having a hard time. I would recommend something soothing and comforting.

If it's at all possible to get her up to the idea.
If I need to chill out to deal with life, I put a drop
Of lavender oil at night underneath my ear lobes.

I have done this for my friends before to cheer them up.
I get them a basket of lavender stuff.
In the basket I add an assortment of organic teas
like, camomile, green,ginger,Earl grey,moringa,dandelion.
You get the idea, make sure that she doesn't have any health issues, none of my friends do.

Also, you can have tea and cookies together.
I love my friends dearly, they are the best.
I love to do anything to make them feel better, or just to show them that I care.

Would need more detail to respond.

Talking is all you can do. You know this person very well. Only you know what to say,which angle to use, at the end just tell her that better days are ahead.

Listen... offer to listen... sounds like you already are... sometimes people just need to vent. I hope she comes out the other side of whatever it is soon!