I had similar problems with my 5-year-old son (but like your daughter, he initially loved it). Your post is from last year, but others may benefit from my input...
Part of the problem was that these were his first "real" daily sit-down school lessons, and so there was an adjustment period that we had to work through during the first few months. He needed to learn expectations for homeschool lessons, and that certain behavior would not be tolerated (just as it would not be tolerated in a classroom setting).

BUT the other thing that helped a LOT was breaking each lesson into 2-3 shorter lessons. Each whole lesson was too long and too much information for him, regardless of whether the material was easy for him or hard. A 5-year-old may not be able to sit through more than 10-15 minutes, depending on his/her interest level. Does anyone else actually do an entire Level A lesson in one sitting?! I can't imagine it!

So, we developed a nice rhythm of 2 Level A lessons per week, broken down into 4-5 mini-lessons. When I can see he is needing more time to absorb a concept (because of crazy behavior, random guessing, and/or frustration), I slow down and spend a few days just reviewing in a fun way, playing math games, etc. (He definitely needed more time to learn to recognize quantities 6-10, and he still needs review sometimes on differentiating 4 vs. 5. We also had to slow down recently on 10's vs. 1's.)

We are now almost halfway through the year and are doing great, he enjoys it. Occasionally I still get the crazy behavior, but I'm better able to judge now whether it's a discipline issue or whether he is having trouble with either the length of the lesson or the difficulty of the material. And, it's okay to stop a lesson short and reassess the situation for tomorrow if need be, as long as you do it in a way that does not excuse the behavior.

A final thought -- make sure you aren't doing any other lessons right before the math lesson that require much mental concentration. Instead, have storytime, art, free play time, or running around the backyard. Also, I chose to not also begin teaching him reading/phonics at the start of the school year when I began math lessons, but to save the reading lessons for later this year or maybe even next year (or you could just wait a few months, until you're in a comfortable rhythm with math; or, start reading lessons first and wait on math, depending on what your child is more interested in). It's a lot for many 5-yr-olds to take in, especially boys (I know many non-homeschoolers who are waiting until their boys are 6 to send them off to kindergarten, because the boys can't handle how academic K has become).