It's not just weight to consider, but also age and body condition.
The bigger, the better. Yes.
Some girls just never exceed 1200 grams. They're just generally small animals and can breed just fine.
You have to look at body condition on top of weight. If you have a long skinny female at 1800 grams, I would not breed her. I find that to be a poor breeding candidate where as a 1200 gram short and chunky girl would be fairly better. That short chunky 1200 gram girl has better fat reserves to endure the breeding season.
I have 2 girls of breeding size. One at 1950 grams and the other at 1400.
I'm only breeding the 1400 gram girl because she's a short chubby girl. She has good fat reserves. The 1950 gram girl is extremely long and skinny. She has no fat reserves and I wouldn't feel comfortable breeding her yet till she bulks up more.
A girl who isn't in prime condition will probably slug out or possibly become egg bound.
You can try to breed her in a year if she had good body condition, but she might not take if she's not sexually mature yet. And that's the age portion you have to factor in.
I know a lot of the larger well known breeders start breeding girls at 1200 grams.