Hi Marie,
Welcome to you and Maya. She looks adorable
My youngest girl is 19 weeks so is a similar age but we got her at 8 weeks and she is fairly bombproof. Generally a pup is open and receptive to new situations but as time goes on - usually around 14 to 16 weeks, they become more cautious to new situations and people.
My first mini, we got at 12 weeks and by the time she had her jabs and was able to get out at 16 weeks we had lost that socialisation period. We had to take things much slower with her and to be honest, even now she doesn't seek out the company of any other dog except our other mini and it took a little work to get her to be happy walking past strangers on the lead but we got there in the end. She will still show anxiety in the house when anyone comes in apart from the 4 of us who live in the house.
My in-laws, who we have round for a couple of meals every week took about 8 weeks before being accepted (you may think being the in-laws that's a good thing) but she will still bark to let us know of their arrival.
I'm not at all suggesting that Maya will be the same but try to ensure that you don't push her beyond what she is happy with. Find a friend or neighbour with a calm dog of a similar age and meet up at a park and let the dogs find the distance that they're happy to be at and you'll find in time (or maybe immediately) that they will be playing.
Don't let anyone force themselves on her, make sure that she approaches them (if she wants to). Obviously a good way is to lure her with some tasty treats but they shouldn't try to stroke her or lift her unless you tell them. You'll know whether she's comfortable in the situation.
Put the work in with Maya now and you won't be disappointed. The mini schnauzer is a wonderful companion. Just don't expect to have any privacy anymore
she is our first schnauzer (although my husband had a giant schnauzer as a teen) so any advice with do's and don't's is very welcome 
