I'm feeling like your GF right now and I am about to tell my BF the same thing. I'll tell you why she/me feel this way...

The intensity and stress about feeling depressed makes us feel bad enough. Knowing we aren't in the mood to be with anyone adds a layer of guilt, no matter how much the partner emphasizes "it's ok if you need to be alone". The hint that you are there, waiting around add to the depression. (this is what i'm working out in my mind this week).

So, I'm like her, I DO NOT want to lose my BF and I know i'm asking a lot for a "break" but on the flip side if I don't ask for a break, I'd have to force myself to spend at least a 2-3 dates per week with him and I. just. don't. have. any. emotional. strength. No strength to fake a smile, or to fake a conversation, fake listen, fake hug, kiss.... doing so aint gonna make me feel any better and faster.

Therefore, the time apart is better for me/her in the end. (I think).