She'll mature in her own time, having a litter will do absolutely nothing to help in that regard. In fact it will be of absolutely no benefit to her whatsoever to have a litter and there are plenty of risks associated with breeding.
Breeding responsibly takes a huge amount of time and effort, plus a not inconsiderable amount of money.
What about your bitch is going to attract decent stud dog owners? Is she proven in any measurable way? Do you show her? Work her? Do any dog sports? PaT dog qualifications? Anything? Are her lines exceptionally rare? What sets her apart from the countless other pet GR bitches producing puppies?
You also need to look into health testing, not just having it done but understanding the conditions and what the results of the tests mean in terms of breeding. At the very least she'd need her hips and elbows scoring, a BVA eye test (repeated annually) and a gonioscopy (repeated every three years). There are also multiple DNA tests necessary; two different types of progressive retinal atrophy, degenerative myelopathy, ichthyosis, muscular dystrophy and neuronal ceroid lipofuscinosis.
Do you work? If so will you be able to take enough time off work so you can be there with her when whelping is fairly imminent and then with the litter until they go to their new homes?
On top of the costs of health testing you'll need to purchase proper whelping equipment, your bitch would need extra food during pregnancy and whilst she's feeding her litter, there are vet visits, worming programmes, all the food for the puppies, the extra power you use for heating and the vast amounts of washing you need to do. You need to have a good amount of money on standby in case of emergencies, breeding costs are rarely (if ever) covered by pet insurance and something like an emergency c-section can easily run into the thousands.
Are you prepared for the sheer amount of work rearing a litter is? It's not all puppy cuddles and letting mum do most of the work. The cleaning and washing and feeding is endless. On top of that there's all the work involved in preparing puppies as well as possible to go out into the world and be well rounded individuals which isn't just giving them loads of toys and getting them used to the hoover. Can you cope with the sleep deprivation? You need to keep an eye on the bitch and litter which means sleeping next to the whelping box and checking them regularly through the night.
Will you be able to provide the necessary back up to your puppy owners? That means supporting them when they're struggling, advising them on feeding/training/exercise/worming/etc. and either taking them back should the owners no longer be able to keep them or at the very least being heavily involved in the rehoming process.
Even when you do absolutely everything right, things can still go wrong. Would you be able to cope with losing your bitch and having to hand rear the puppies? Or losing both? Or ending up with no puppies and a very depressed, lactating dog to nurse?
More often than not bitches whelp absolutely fine but you do need to be realistic about the risks you would be taking with your bitch and whether it's worth it just to produce another litter of a breed there is absolutely no shortage of.