I've never heard of anyone else who's had a postpartum Group G strep infection apart from me!
I was readmitted on day 4 after horrendously long labour with DS1 with high fever and they discovered it was a Group G strep infection. I was in for 3 days with IV antibiotics.
Then on day 11 DS1 developed a really nasty fast-spreading cellulitis (soft-tissue infection) on the buttock and was very, very ill. So he was treated for Group G and had 11 days in hospital on IV antibiotics, plus an operation to drain the pus that formed at the original infection site.
When I was pregnant with DS2, I had weekly swabs from 36 weeks to check for Strep G and was induced at 40 weeks with IV ABs during labour, then kept in for 48 hours so that DS2 could be observed.
All my swabs during my second pregnancy were negative and DS2 was fine. But if you have had a streptococcal infection you may want to mention it during any future pregancies. Your baby did not become ill, but it could be a risk for another baby.
They were extra careful with me because of the fact that both I and the baby had been ill. I guess the swabbing and the ABs during labour are a lot more cost-effective than 14 hospital days (including intensive care), 1 operation, X-rays, ultrasounds and lumbar punctures,etc.
This was 8 years ago, and I have tried to research Group G strep but haven't found much at all. I don't think it's a particularly common cause of post-natal infection.
If I were you I would take the antibiotics just to be on the safe side.