A friend suffering with depression

Absolutely agree with Oopsadaisy & Pascal keep sending chatty messages and let your friend know you still care about her even if she can't respond at present.
I hope your friend recovers soon LRavenscroft

Yes, you’ll be doing the right thing.
Even if she doesn’t reply, she will appreciate knowing that you are thinking of her.

She probably doesn’t know what to say; or thinks that you won’t want to hear what she does want to say.

Depression makes you feel worthless, she might feel that she isn’t worth your friendship.
It also makes you say dreadful things to your inner self, if you know what I mean.

You sound like a lovely friend

You sound like a lovely,caring person I'm sure that she'll find comfort even if she isn't able to respond. Depression is ghastly

Thank you both very much for your response. I'll keep up the messages to show her that I care.

I think this is the time she most needs to be reminded that you care about her and are thinking of her. I would accept that she is ill and can't keep contact but continue to send her regular short messages telling her you care until she is able to respond. And bear in mind that depression can last for some time.

Can you send her weekly/ monthly emails? Just a friendly chatty one about your day to day doings, that let her know that you are still thinking of her?

Hopefully when she gets better she will look back and see that you were still there for her, it might make it easier for her to get back to a normal friendship with you.