'Being there' means more than recognising a significant other is in a batte with depression.

As with any mood disorder (depression, anxiety etc), there are in fact things one can do:

Based in my own experience I want acknowledgement and validation more than sympathy.

Acknowledge that the mood exists. Validate that the mood is real. It doesn't matter whether you think the mood is justifyable the mere fact she is feeling it makes it real.

When I have been having depression and anxiety physical affection is not going to make me feel better.