Especially in a world where people pick up their whole lives and relocate for jobs. Recent joiners aren't getting any sustainable kind of severance either. The idea is if you're hiring them you have a minimum commitment to support their success.
Yes she was an obvious fire, but it's also the organization's fault. Enterprise deals also take way longer to close than that...
All that said, salespeople can and do move jobs a lot. I'm sure she'll be fine.