Mr. Wings, according to the Merck Vet Manual, they are in standing heat bout 7 - 14 days....I believe from start to finis is roughly 21 days.....there are usually several days before a bitch will first stand....and then several days of going out of heat after the last day they will stand for a stud to breed them.
So, ya really need to have an idea of when Mollie first began exhibiting symptoms, i.e., licking her genitalia, etc. And, ah, sir....if you're changing her diapers, you can probably be safe after 7 days no no bloody spotting.
Livestock, as well as humans, have to go by the law of averages....individuals can go either way.
In any event, you be sure to give little Mollie lots of love and playtime, ya' hear!
Naw Ringy stayed thru all that. She knew better'n ta leave me wid the Bitch if she was actin up. Heheeheee. Durn dog was supposed to be over this on the 31st. Thas today ain't it? Why'n she better?