What's going on here?

[TB9]

If you have been rocking to sleep to extend naps then she will wake at the 30/35/40/45min mark and need you.  I suspect 3 or 4 (or even 5) days of sleep training just isnt long enough to break that habit 

Keep up with the sleep training, make sure the A times are right, and you will see progress.  But LO is young and used to having you help her back to sleep during naps, so LO will still need you to help using shh/pat for awhile 

[rochelleperales]

I am ok with continuing the sleep training. It's trying to find what her awake time is that is driving me bonkers. I know that alot of LO'S have a shorter A time in the a.m then the A time gets longer throughout the day. I don't know if I am pushing too much for the first nap or not enough. With my 2 yr. old, he was taking two hour naps at 5 months with 2 hr awake time. I had hoped that she would do the same. We have been dealing with 45 min. ( now 30 min.) naps for 3 months. I really need someone to look at my EASY and see if I am pushing too hard or not enough.

[TB9]

I think you are the best judge of that  hun...is she waking happy?  Is she able to make it a full A before she goes down for another nap?

If you have been deaing with short naps for a few months I would say you need to push for more A time.  BUT I also found the 4-6month age the hardest time to get good naps because often one feed isnt enough to get through a decent nap.  I thi k there is a developmental leap around 6months too    So it may not even be an A time issue...

Every LO is different, not all LOs like the shortest A in the am, some like even A through the day, some like shorter A in the pm.  I think sometimes you have to go by cues (if you LO gives cues) and see what that gives you.  Do you have cuus to go by?

[rochelleperales]

Her cues are all over the place. Yesterday she was getting fussy at 1hr 30 min of awake time in the a.m. Today she was at 2 hrs. before she started showing any cues. I am not sure at 21 weeks what her awake time should be....toward the 2 hr range or 2.5 range or in between. I guess I should pick one and stick to it for a while, I just don't know what. What I don't understand is why she cant go back to sleep at 45 min. (or 30 min the last two days)if she is able to go to sleep independently with no help from me. She should be get through the transition. Its frustrating because I have done so much sleep training, and I am glad she can go to sleep independently, but I thought we would be at longer naps by now.

[weaver]

I'm sorry you're so frustrated!  I think you should give yourself a day off naps, and try not to worry.

The thing is that short napping is really common between 3-6 months, and that's with perfect A times and everything else being totally normal.  It is probably nothing you are doing *wrong* so don't beat yourself up.  If she's waking up after 30 mins, then I would say she's OT, scale back the A times, listen to your mama instinct and put her to bed when she's tired. A times around 2 hr- 2hr 30 for this age.  Be guided by her history. Do you think she's high or low sleep needs? Or probably average? 
Average A times- BOOKMARK ME!!

Having said that, you've raised a couple of questions in your various posts so let me do a bit of a round-up:
* food: some LOs on 4 hourly feeds find that they want the occasional snack to set them up for naps, just a bit of extra.  My LO2 around 5 months did 4 hour EASY but usually had an extra bit of milk about ten minutes before her afternoon nap.  Not another feed, just a bit more milk.
*swaddle: you may wish to reintroduce it, if you suspect you've weaned the arm too early.  Don't worry about it, lots of LOs love being swaddled and stick with it longer than you'd anticipate!
*self-settling and transitioning are not the same thing.  Many, many LOs are able to go to sleep happily alone but need help to learn how to transition.  You can sit with her and pat her when she stirs, you can try W2S, you can get her up when she wakes and put her in a sling/buggy/car seat to do another nap.  But you will probably have to do something if she has a persistent problem with short napping, and particularly if she had a rocking back to sleep prop.  You need to teach her something else instead of that prop (as Tink already said).
Teaching Sleep- Tips from the boards

Have a read of this, a bit of a morale booster:
short naps at 3-4 months? Take it easy, it will get better!

The last thing to say is that we're all volunteers here, and in different time zones, so it may feel like your post is not getting attention.  But it will, it just takes a while sometimes!