I think many people are nuts these days. They want their kid to be the oldest for some reason (better in sports since they're taller, first to drive among friends, be older when going to college, etc). All silly reasons, IMO, to hold a child back a year. Going to college when 17 is no big deal - in many countries, and even certain cultures here in the US, you get married at 17 so certainly a 17 year old about to turn 18 can handle living in a dorm and getting himself to class on time!
All my kids have summer birthdays - July and August. The cutoff date in IN is Sept 1 so that is why Sept birthday kids wait a year. My son's birthday is mid-July. It was NUTS his kindergarten year. He started on time, right after he turned 5. However, he was in class with 7 YEAR OLDS by the end of the kindergarten year (kids with April/May/June birthdays)! NUTS. I hated it. His TEACHER hated it. I'm sorry, but 7 year olds are in 2ND GRADE, not kindergarten! My son is now 7 and in 2nd grade. His teacher told me it's been getting worse and worse... after 20 years of teaching kindergarten she was about to quit and get a job at a preschool. She teaches kindergarten because she likes 5-6 year olds - not 6-7 year olds. I just don't understand why so many people can't follow the rules. If more people stopped holding their kids back, the teachers wouldn't have to deal with a 1-2 age range in the classroom -- that is disruptive to them and hard to teach because of the difference in maturity at those ages.
In many states, the cut-off date is Oct, Nov or even the end of Dec (following calendar year) so it's very common for 4 year olds to be in kindergarten and turn 5 during the school year. These kids do fine. Heck, most kids are in a full-day preschool program due to working parents before starting kindergarten so surely they can handle a full day at kindergarten. (we have full day K here). We all know that young kids learn best - so make your kid wait until he's older to start school? I just don't understand that at all.
Anyways... send your daughter. She's 5. She's ready. The kindergarten teacher will expect her to act like, well, a 5 year old! That means working on issues like standing in line, sharing, sitting still and getting alone well with others. Kindergarten teachers dont' expect those things to be mastered before starting school - that is what kindergarten is for.
When my son went to kindergarten, I was expecting the worse. He was the youngest (by far) and had soem developmental delays. We later found out he had ADHD, anxiety issues and Asperger's... guess what? He thrived in kindergarten! He did very well, and continues to do very well. He often complains that his classmates are so much older than him but we just explained the reasoning - we sent him on time and didn't hold him back like other parents did with their children.
My oldest daughter will turn 5 at the end of July. She's signed up for kindergarten and is really excited about it. She's ticked that one of her best friends at preschool won't be at kindergarten, though, because he mom is holding her back a year (a May birthday!!). Our youngest has a mid-August birthday and will go to kindergarten on-time, too.
ADDED: I just read through some comments... a few people have said "no one ever regretted delaying their child but some regret sending early". What a crock!! I know several people who totally regret holding their kids back a year once their kids were in school a few years. I know many teens who HATE being so much older than their classmates. I haven't talked with a single parent, though, who regretted sending their kids on time! Don't make generalizations.