Good on you for wanting to help your friend. :hug1: Some folks avoid depressed people like they’re going to catch plague from them.
I don’t know about what to say but I know a little bit about what not to say. Yep, gently encouraging her out of the house is great. I suppose my “advice” is more long-term, if you do end up spending time with her over say months or a year or so.
(There’s all the usual rubbish like, “snap out of it”, “get over yourself”, “pull yourself together”, “other people are worse off than you” that I assume you don’t need to be warned off saying - you wouldn’t be going out of your way to help this person if you thought like that.

)
I spent most of my childhood depressed and have had two major 4-5 year long bouts as an adult. After the first bout I felt such furious resentment of those who were
supposed to care for me that I endured the second “in secret” without any treatment or medication because treatment would have meant I couldn’t hide it from them and I sure as heck wasn’t going to let them anywhere near my illness a second time. That was the wrong thing to do but there you go, long story. The reason I felt such fury was that one of them in particular tried to impose
his conditions and
his timetable on
my illness and
my recovery … there I was at the beginning of something that had been brewing all my life and would last for another five years, and I got, “well, I’ve sat here with you for two hours and you haven’t cheered up at all so I’m clearly wasting my time and I’m going to go and wash the dishes/do something more important that isn’t a waste of my time/leave to go home now.” Now, as you’re not in a BF/GF relationship with this person, nothing so intense will happen … but I learned that one thing you can’t do with a depressed person is put your conditions on how they react and cope and deal with it and eventually heal. You must respect that it is their illness to deal with as best they can.
Dealing with a depressed person can be real hard work, and it would have been OK with me if abovementioned person had said, “look, I’m finding this heavy going, I need some time away right now, but I’ll be back, see you then”. The last thing a depressed person needs is to be made feel that relationships they value are dependant on them jumping through someone else’s hoops, or that to be loved and acceptable they have to pretend everything is now rosy. That’s one reason why Bible study or going to Mass might be a good thing - it gives her other company rather than a close one-to-one relationship and might help dilute that sort of concern.
I’d really like to emphasise that the fact that a depressed person continues to be depressed does NOT mean for a minute that your friendship and encouragement is not having an effect. It can be like clutching a bit of floating timber in the sea - you’re still in the sea of your illness with no rescue in sight, but that bit of wood is what’s keeping you afloat! If you’re going to help a depressed person, though, you have to get rid of any idea in the short term of “expecting results” in your terms. And it’s absolutely OK to need time away from the friendship but that should be expressed in a way that doesn’t make the depressed person feel they have lost your support because they haven’t fixed themselves up when they “should have”.
HTH, though you probably don’t actually need any of this advice. I wish I’d had someone want to help me in this way when I was at rock bottom.
