I have to agree. Even if she is old enough she is under stress just adjusting to her new home. If you feel you need to breed b/c you have heard the stories about females that die, eggbound etc. if you DON'T breed I can attest to that not being true. Luna is over a year old has successfully laid two clutches of 42 infertile eggs and is just fine.
As Carlton points out you should let her adjust and YOU too. Being a new, inexperienced (no ofense intended) cham keeper I think it would be very risky for you to jump into breeding. You then have to find an appropriate male and also keep in mind that once those eggs hatch you will need to provide for them until they are a few months old and then find good, safe homes for them. Just enjoy her 
lele
>>I can't believe the breeder doesn't know her age. Sounds very careless. You've only had her 3 weeks, she has barely settled into a new situation, she doesn't sound full grown especially if the breeder can't seem to tell you if she's mature, and you have no idea if she's still rapidly growing or maturing. What is the rush to breed? Give her time, watch her growth rate (or lack of growth) by weight for a while, and then when you are sure she is healthy and acclimated think about breeding. It is always best to be conservative and you run much less risk of killing your female due to poor reproductive condition, injury, egg binding, calcium deficiencies, and stress. You don't have to breed to be considered a successful cham keeper. I'm sorry to vent a bit, but females are more than just breeding machines. Breeding is a huge energy expenditure and the riskiest thing a female does in her life. Give her a chance to have a decent life and be successful.
-----
0.1 veiled - Luna
0.2 house geckos - Gaia & Tia (both MIA 
0.2 felines - Kyndra and Líta
1.0 African Clawed Frog (for summer)
0.5 Mad. Hissers (for summer - all girls, no little ones, whew!)