She is very young to be away from her litter mates, the only time I've had one that young was when we took on Oldgirl as an emergency rescue and it does make things harder in lots of ways.
It's a shame she's been taken away from them so young, as much of her social skills learning, bite-inhibition etc would ordinarily have been done through play and interaction with her mum and siblings. Difficult situation if mum had had enough, but imo, really the breeder should have kept the litter together, but away from mum for another week or so.
She'll need to start puppy classes as soon as she's cleared to start mixing with other dogs and in the meantime needs to be carried everywhere and introduced to lots of things for socialisation purposes.
I can really understand why you don't want her to go down in your garden till she's vaccinated, under the circumstances.
If you want her to go on grass when she's older you could create a litter box for her - they do it a lot in America, where dogs often live in apartments, but people still want them to 'go' in parks etc.
You basically need some sort of plastic tray and get some turf cut to size to fit in it and reward her for going in it. If you have a back porch area it would be a good idea to put it there, so it's as close as possible to the garden, then when she's had all her jabs and is cleared to go out you can just move it outside and to whichever area of the garden you'd like her to toilet in. There are a few videos on youtube. You can see one in use in (although the video is actually about home-alone training). You can also buy ready made litter trays, but they tend to have astro-turf, rather than real turf in, which means you would still end up having to teach her to go on real grass, although I suppose you could possibly buy the tray and put your own turf in it.
Alternatively, if you have a patio you could buy some parvocide disinfectant give it a really good scrub and fence off an area for your pup to go on.