potty learning in general question

so we've been part time practicing EC since ten months old and now at 18 months, we spend most of the day in panties, accident free.

However, when she does have an accident, she gets SO upset.  I mean, very, very upset.  She's never been punished for having an accident, we don't make a big deal over it, just clean it up and change her and that's it.

But she is almost heartbroken over it, it seems.  Almost as if she's embarrassed about it.  It gets me upset seeing her so upset too.

Any help or ideas?  Is this just a natural part of PLing?