If she has no experience, and doesn't know the going rate, and she works for someone else, she might settle for something like $0.75 a minute. If she has experience does her research, she can expect to start at $1/minute, or up to $1.25 a minute, and can expect to get raises as she proves her value to the company by keeping men for longer sessions, and keeping her regulars, and by being reliable.
If she works for herself, she can expect to make $2.50/minute to $5.00/minute based on how much she feels she can get away with charging. She'd be part f a camming community, and should charge the high-end of the average range of prices there. The more of a niche she can fill, the more she can charge. That is, if she knows how to manipulate fetishists, she can really make bank.
The kinkier a guy is, the more he's used to paying to get his desires satisfied. Foot and leg guys, guys into odors and scents, guys, guys into body worship, and others are willing to spend lots, and sometimes buy your old sockings, panties, bras, shoes, etc or buy you new stuff to model for them. You just have to know how to ask. (I'm a phone dominatrix. I can make this happen, I KNOW even a bad cam girl can do it.)
The downside to working for oneself is that you MUST do your own marketing, and sometimes that's not only boring, but tedious. It costs money upfront sometimes too. The plus side is you make more. On the other hand, the downside to working for an employer is you'll have a salary cap, and you may have a more rigid schedule. On the plus side, you may not have to get involved with marketing, and even if you do you won't have to lay out any money. Also, you're more likely to see customers faster.
Either way, she should know this:Those images of her, naked, stripping, playing with her pussy, or whatever else she does are FOREVER. There is nothing to stop a viewer from saving screen captures of her stream. Nothing. If she's comfortable wth that, she can make bank.