Update to DD1 hitting DD2

So I really appreciate all the responses to my earlier post - they really are super helpful!  And it's comforting to hear that this has happened to pretty much *everyone* before....Anyway, it's still happening, even more.  She's been hitting her sister probably 5 times a day since... whenever she gets a chance.  I'm getting faster at catching her before she does it and put her directly in time out.  Hopefully she'll catch on and this phase will soon pass... so wish me luck.  Meanwhile I'm frantically trying to rig up safe places for DD2 throughout the house.  Thanks again though for all the support!