<human>: Can you provide a brief rundown of the text in within 3 sentences?

Hey there /relationships. Here's the skinny: me, 23 year old guy, her, 24 year old girl, us, been dating for about 2 1/2 years. Pretty simple question: over the past several months, her depression has been getting worse. She was diagnosed with it when she was a teenager, but has been off medication for a few years. It's been in the background for most of our relationship, but never bad enough to ever really affect anything. 

Recently, however, it's been getting noticeably worse, and affecting both my mental health and our relationship. She may attribute our issues to other factors, but in my mind, at least things would only be made better by her not being depressed on top of everything.

I've talked to her about her depression, and she's very resistant to seek therapy. She has access to it, and has made the "first steps" a couple times, but never gone through with it. Whenever I bring it up now as something to revisit, she accuses me of being condescending and only making her feel worse. 

I feel at a loss for what to do. I think ultimatum's in general are super lame. People shouldn't order or threaten other people, much less their significant other. I love this girl madly, but I feel like I have to at least try something drastic to jumpstart her into action. 

Is giving her an ultimatum of a week or two to make actual, actionable steps towards therapy fair (the alternative being breaking up)? Is there another way I can approach this (any input from people with SO's that have depression would be great)? I really, really don't want to break up with her, but I feel cornered.
<bot>: Girlfriend's resistant to seeking help for her depression, and I'm thinking of issuing an ultimatum to jumpstart her into it. Bad decision?