First of all, I probably did say my goal was to potty train by age 3 but this may not be realistic for every child. I have never read, "The Everything Potty Training Book." I think I've read the "My Big Girl Potty" if its the one that is written for children like a story book. My kids really liked this book.
I believe children will be ready at different times even though we would love for them to be potty trained early. Also, I think children could use going to the bathroom as a power struggle with parents because they are in control of this. Maybe she just needs to know that it's her choice to go to the potty and let it be her thing.
You may ask her if she would rather go back to wearing diapers during the day until she is ready to go potty every time in the potty. If she does then go back to diapers. Don't let it bother you one bit. Maybe it would be good for the whole family to take a break because it sounds like the fun of being a big girl is gone for both your 3 year old and mom and dad. If you are frustrated with it then your child is probably frustrated too. In the Love and Logic Magic for Early Childhood book it says, "Like any task we're expected to perform under pressure, potty training becomes an undesirable chore." pg 35 If your child wants to continue with her big girl pants then one idea is to lay low and tell her that you know she is a big girl and you have every confidence that she can go to the bathroom when she needs to. Tell her you are going to stop reminding her and that when she needs to go to the potty she can choose to take you with her or go by herself. Take out the reminding and you being extremely anxious about it. Another thing that helped my first was when he had an accident I really had to not get upset (and believe me it was hard) but I instead talked about how sad it was. I like how Love and Logic words this response: "Oh, you had an accident! That's too bad! I love you, Sweetie." Then you can make them apart of the clean up by asking them to put their clothes in the laundry and getting you a rag to clean it up, etc.
Now the nighttime water (or in other terms bedwetting) is a completely different story. My oldest was 6 or 7 before he stopped wetting the bed. We tried everything. After consulting our physician on many occasions at well visits he recommended a bedwetting alarm. This really worked. In the instructions of the bedwetting alarm it talked about how children are not doing this on purpose, they simply sleep so soundly that they don't wake up to go to the bathroom. It is a physical response and their body has not learned to tell their brain when they need to go. The alarm requires parents to be extremely involved but it was well worth waking up a few times at night for a couple days and taking him to the bathroom.
It doesn't work to not give them any water hours before bedtime or waking them up before you go to bed to go or lectures about wetting the bed, or even having them clean the mess up. Believe me we tried all these things. There is also medication and herbs that you can try but I really didn't want to add other side effects that go with Meds. The thing with the alarm is they really need to be a little older--I think the age recommended was five. In the meantime don't sweat it--after I have talked with other parents this is really common for a lot of children.
I know they are really expensive but you can get overnight diapers for bigger kids. I would just use diapers if they still will fit your girl. I also put water proof sheets over the mattress so it doesn't get ruined and I also put a waterproof pillow case over the pillows.
I hope this helps a little bit. But try to look at the long picture here and realize that as long as they are potty trained by kindergarten you will be just fine. =)