
Pugs are often a hard breed to breed. Not trying to sound rude but if your asking this question it may be in your girls best interest to Waite and do more research before trying to mate her. Don't get me wrong it's good your asking questions but Alot can go wrong so you need to know what can go wrong at each stage, how to spot it and what to do about it. I'd suggest 'the book of the bitch' alot of good information.
Bitches can varie when they are ready, some are ready early other much later. If distance to the stud is far and you need to know for sure you can progesterone test her. You vet can send blood off for testing which is more accurate or do an in-house test with it but its less accurate.
If you haven't yet you should also get her hemivertebrae checking as well before breeding. Don't know if you have allready done this.