Don't beat yourself up over it, you did nothing wrong. Sometimes cat's just do things that later they find out they shouldn't have done (kinda like us hoomans sometimes). Boo will probably heal up without too many problems and I'm happy to hear she's feeling better already.

Two of my cats had some limping episodes in the last year. Both of them happened when I wasn't home so I can only assume that they tried to jump to the high cabinet and missed or something. Their vet said that they probably tore some of their ligaments and put them on Dasaquin for a month or so, I was told cats tend to heal up easier and faster without the surgery unlike dogs. The limping healed up and both are now tearing around the house like nothing ever happened an no sign of limping.