It is much easier to cycle through serious, long-term relationships or re-marry than it is for a perpetually single person to enter the market. People partner up and break up in cycles. Your aunts and other taken people around you just so happened to have been taken when the market was sparse and became single again at the opportune time. Plus, because they've been seriously partnered or married most of their lives, they are always around commitment-minded individuals by default. I've noticed this with my married and partnered acquaintances as well. They've always been in some sort of relationship. Past a certain age, a perpetually single woman or man has a slim chance of gaining entry into the market unless they buckle down and make it a priority. Most perpetually single men are single for a reason. Quality men don't stay single for long and they gravitate towards women who have always been in a relationship it seems.
But this is nothing new. Society has always acknowledged that there would be a lack of men suitable for marriage and family-- so in the past the outliers were sent to war, took up jobs that removed them from mainstream society (whaling/cattle-handling), or lived as outlaws or pirates. Now they are free to roam as freeloaders and effboys
. Numerous, but not suitable for courtship. So the ratio has always been unfavorable for women. Back in the day, unmarried women either entered convents, took up a trade, turned to prostitution, became entertainers, or settled for being a mistress or courtesan like OP's friend. Unmarried women have always been numerous in western civilization, it is only now that they have a voice.
OP, when this ends, I doubt your friend will be able to bounce back emotionally. She's playing a dangerous game. I hope she wakes up.