There are parts of her description that don't sound like depression, so it would be best to see a doctor to rule out anything else. I really admire people who can decide what they need in life, what they want to do and change what needs to be changed but the truth is that it isn't always possible. Sometimes things can't be changed and sometimes depression takes away the strength we have to make those changes.
I was struggling with low level depression for years. I lost weight, I focused on the positives, I went for walks, I applied for jobs and when that didn't work I did extra courses to help, when that didn't work I applied for a doctorate and looked at what other paths I could try and take. Mean while life kept piling sh*t on top of me and I got to the point where I was suffering from severe depression. I no longer had the motivation to get out of bed let alone change anything. I worked my butt off and yet I didn't get anywhere and nothing got better. The more I tried the more helpless I felt. If you can make changes and it helps then that's great but some people need medical help. I'd gotten to the point where I needed that medical help to level out the chemicals in my brain and then I could start to move forward and make changes myself. I don't think it is always the case that people can 'snap themselves out of it' and if you can't, it does not mean that you are weak. Depression is a strong and crippling thing. It's different for everyone. One in three people will suffer clinical depression in their lives so if you do you're not alone and you're not weak, you're normal and have just succumb to every day stressors or sometimes your chemical balance becomes off (and you feel depressed even though everything in life is fine) and that's ok. It's fairly normal for this to happen at some point. All we need is the strength to seek help if that's what we need.