I find it really odd (incredibly beyond words odd to be honest) that when she goes through these periods of low mood she genuinely believes it's a collective thing, everyone else must be low also rather than accept it's something within her "i spoke to my friend and she's in a funk too" as if that explains it all and absolves her from taking any responsibility for her own wellbeing. Depression is not a cold, it's not something that's doing the rounds, something you can catch.
Although it won't fix things for her, i honestly believe if she didn't live like a slob she'd feel so much better. The matted greasy hair, bloated shiny face and the same crumpled faded sweatshirt for 3 consecutive days at a time... anyone would feel down if they put no care into looking after themselves.
The best thing she could do for her mental health is come off social media and youtube.
I'm watching the vlog now, oh what a surprise she "was talking to a friend and she said..." my eyes rolled so hard to hear that
How can she have sad when she has this all year. I tell you what mik, look back on the vlog where you described having to spend the summer holidays with your own children as like a lockdown and how happy you are for September to get rid of them, that will remind you that this is a year long moan and whinge. Not seasonal by any stretch