So here is some advice but first let me say, that sucks and I'm sorry. This happens and the fact that it happened to you and your friend today sucks even more. Now that being said your friend at least is entitled to much more than a refund. Assuming she had a reservation, checked in before the cut off time, and wasn't flying standby originally, she was, in airline lingo, involuntarily denied boarding.

Therefore she is entitled to certain rights. What happened is not illegal, the federal government says it is not, however, they do agree that she deserves compensation because, essentially, a contract was broken. Bottom line if they can't get her to her destination by a scheduled means within two hours of her originally scheduled arrival time she is entitled to 400% of her one way fare or $1300 whichever is less. Keep in mind that this is ONLY compensation for being denied boarding. She is also entitled to a full refund of the one way ticket (and a good argument can be made for the return ticket too since the reason for travel is now moot) assuming they can't get her on another flight or she chooses not to travel now.

Keep in mind that she is also entitled to the compensation in CASH or check. Don't let them talk you into travel vouchers if you don't want them. Travel vouchers don't cost them money, cash does and I'm assuming she doesn't want to fly southwest anymore. Unless their customer service agents aren't complete douches they WILL try to negotiate compensation that is more advantageous to them. They will probably offer her less than she is entitled to or will insist that they can only give it to her in flight vouchers. If this happens and she wants cash continue to insist and if necessary keep asking to see managers until you find someone who knows the rules. A quick google search on a smartphone can mean the world here because it shows you know your rights.

That being said nothing is final until she signs on the dotted line. What is happening is the airline is negotiating to buy back her seat after they have already taken it from her. Technically they can negotiate the sale via whatever medium they both can agree is acceptable, she can settle for bubble gum if they both agree. The cash option mandated by the government is the final option specified by the government if they can't come to any other terms. That being said it is possible (though unlikely that they may offer more compensation than legally required, maybe even pay for the game tickets (highly unlikely but possible). Therefore if she gets a better deal she should absolutely take it but know the cash option is always there. Once she signs the agreement she agrees that the compensation is satisfactory and that settles the matter. I'll also warn you that the method used to calculate the one way fare is not going to be intuitive, in other words it won't be half of the round trip fare she paid, even less if she had a connection. But given the day she was traveling my guess is that she might have lucked out because it would probably be fairly expensive to fly to SFO today.