If you travel a lot, and you do your travel with the same airline as much as possible, it is absolutely possible - and a frequent occurrence - to get free first class upgrades. Once you you rack up a certain amount of lifetime miles flown with the airline, you get bumped up any time there's an unsold first class seat. Plus if they don't have an upgrade for you, they still give you the first class meal and free booze for being part of (whichever airline loyalty club).
I presume Anna hit the United Million Miler mark while she worked for Sprinklr. However, you have to maintain a certain annual flight miles minimum to keep your status. This is why she takes so many trips even though she's self employed; otherwise she'd lose her status and there's no way she can fit in a coach seat. Frankly I'm surprised she can fit in first, the seats are either molded pods or chairs where it's impossible to move the center divider.