Having the Billy around you should see signs when she is in season - tail wagging, calling, slightly off feed and I'm sure there's more but those are what I look out for.
If I was you I would take it she was in kid and as she's not particularly big we could say possibly one kid, I am guessing your billy is still in the same paddock with Polly so if she did come into season he would do the deed and if she's in kid things should just continue.
My youngest girl (18 months) is quite small but I know she didn't come back into season after being with the billy so I am thinking one kid for her.
Hope all goes well for you - keep us informed with lots of pictures