Hi
I will try to give you some answers
1 - it will take about 3 weeks for her to be "out" of heat
2 - Yes she will be moody - as to the cramps - we can only guess - she knows something is different but she is not a human ( yah right - try to tell that to all us Yorkie owners
) so she is only going thru what nature intended for her. Is there a reason you haven't had her spayed ? Do you intend to breed ? If so I certainly hope you either do years of research in about 5 months or have a good mentor - or just plain do whats best for your baby and have her spayed - Trust me - breeding is not for the faint of heart or novice owner. I am not being mean here - just trying to educate.
3- If you don't want to cause a riot and be the most talked about ( in a very unflattering way ) dog owner at the play meet then you will keep her home and away from there - not to mention the fact that if the time is right and there is a intact male there you will become a breeder no matter what your intention is. Any male within a mile of her will know and be right there.
Also other females will sometimes pick a fight with one that is in heat so definitely keep her away from this play date.
Hope i have helped you and if you want more and detailed info you can PM me and i will be glad to help you all I can -