Lila is now crawling just as much as her sister. They are both sitting (and falling over) on their own.
We're noticing that Lila is more cautious than her sister, which might be why it takes her a few days longer to do the "big milestone" things than her sister. Lila will spend more time and think about what she is going to do before she does it. Zella, on the other hand, is a dare-devil; she'll "Just Do It." [tm] ;-)
Case in point, when Zella decided to crawl, she'd just start trying, and would manage two steps before she would fall. Lila seemed to analyze how to crawl (distance, wind velocity, etc.), and then started crawling four steps at a time before she would fall.
We're still working on baby-proofing. We're considering running bubble-wrap around all the walls, furniture, etc. :-) The thought crossed our mind after Zella's incident yesterday when she was crawling, tipped over, and hit the wall with her head. She cried, but was fine after a few minutes (more so than us).
We'll probably post more pictures after this weekend.