Without a wind down, you need to give her support in falling asleep. But while you're trying something new, you need to do whatever you can to make sure you stick to it. ie: if you choose to do a longer wind down, be sure you do it consistently.
When she's been wound down sufficiently, it's okay to walk out. I have found with mine, that when I walk back in, it deters any progress already made. Some days are good (this morning she cried for 2 seconds, and then asleep), some are not so good (this afternoon she cried for 8 minutes, and I've had worse). Although it's rough on me(and her in some ways), it would be far worse if I went back in there with her crying, we'd have to start all over, she'd cry longer in actuality, and by the time she did fall asleep she'd probably be overtired and have not as restful of a nap as possible. She needs to fall asleep on her own.
In my case, she already knew how to fall asleep on her own, but something-I don't know what- messed her up and she gradually became over tired, and now we're going to fix it, and probably teach her how to go to sleep without the crying hopefully.
Hang in there, if she needs to cry to get to sleep, that's okay. Some are like that. The crying should get less and less every day. Just stick it out. But you have to try it consistently for several days. If it doesn't work, try something else. Just don't get her dependant on you to get to sleep. It'll be easier at first, but something else you'll have to break her of later - the older they are the harder it is - so do it now if you can.
