I probably shouldn't say this but the male is the best indicator, so if they haven't got a clue as to what is going on your girl is pretty safe. Males seem to click to the idea around 5 months I've found. And will try their little hearts out given half a chance.
Mind you I named a 7wk old Kelpie pup Stud because he was practicing all the moves on his litter mates at 7 wks, he turned into a very good stud dog.
Scratch her above the tail and if she presents or stands to you then separate her. If you got male pups over about 4 months old I'd remove her from the first day you see her coming in season regardless. Diary note the dates so you are prepared for next time especially given she is a coated breed.
Get her accustomed to being crated or kept in a separate area of the house or whatever you wish to do so that it is not such a shock to her.
Personally I'd be more concerned with what can get in to her than young puppies, I run hot wires along my already high fences and am putting in a front fence as well.
You could try the pants, but the puppies might see them as a toy and rip them off her.
Years ago I delayed a bitch coming into season because we were traveling. I was advised this was not a good long term solution as she was a brood bitch, but since you never intend for her to have puppies it might be worth looking into or seeing what new drugs are available.