How can I help a friend whose spouse is going through depression?

My friend's spouse is going through a bad depression (they are getting help from a doctor and medication). My friend, however, is a terrible worrywart even when things are perfect. My friend is prone to anxiety and obsessive worrying.

What can I do to help my friend cope? I am scared that BOTH of them going to end up in a depression!

its simple
just be there for her. Tell her to call you whenever you want. or tell you whenever she wants to get together and no matter what you will make time for her. call her often.
but in all of this, dont smother her or something. just keep things light hearted and fun, maybe plan some cute walks or coffee dates together. only talk about her husbands depression if she wants to - sometimes having a really good reliable friend to vent your problems and concerns to helps a lot.

if you begin to notice any signs of depression in your friend, maybe suggest that she talk to that doctor to.

Try to encourage your friend to do things that can give them a much needed break from worrying about their spouse. Just a couple of hours a week doing something that brings your friend great joy can be very refreshing for them. They have to look after themselves first in order to be able to help the spouse. I had bouts of depression for many years until I learned I had a caffeine allergy & a sugar intolerance. Since eliminating all sources of caffeine and limiting my sugar intake (to minimal natural sources only) I have had no more depression at all. Maybe, you could encourage your friend to look into that too.

Just be there for him to listen. Take him to a movie once in awhile. Encourage him that they are doing all they can with the doc's help.

Be there for them but not too much. Offer your help, take them to fun place. A day trip perhaps.

introduce them someone who's life is worst and they will feel better about theirs.