For me, the whole "kidnapping people to take them to a sales event" is what really stands out from Sandra's past. Someone might say something obliviously hurtful in a non-thinking moment, or just be caught up in their enthusiasm for something and not understand how they're being perceived by others, resulting in her comments to the OP (which are nonetheless painful). But the planning and deception involved in telling people they were going to dinner, then insisting on driving them and changing the destination to a sales party? To me that is deliberate and malicious, and nothing less than a complete about-face, abject apology, and visible change in behavior would make me even consider being friends with that person again.
For this and for the heartlessness she has shown the OP, I advise completely dropping her. For the moment, at least--if you don't feel comfortable saying "forever," perhaps decide you're not going to have anything to do with Sandra until your health crisis has passed and you can afford to think about other things again. I would block her on every avenue and ignore any further communication attempts. She's a source of unneeded stress right now and I don't think it would be rude to mute that for the time being, given her behavior.
On a side note, without meaning to derail the thread: I've known a number of people who've been successful with MLMs like Mary Kay, and have never gotten so caught up in it as to be rude. In my observation, the people who are both successful and polite are those who are business savvy and perhaps already have some business experience before they begin the MLM, like women who run their own hair salon and sell MK at the counter. And then there was my friend who got sucked into MK after a bad break-up, spent thousands of dollars on product at once, and was irritated that the co-workers she invited to parties didn't show enough enthusiasm.
I think it really depends on the individual, whether they're prone to rudeness or not.