I have seen males become really aggressive towards a lambing ewe, first repeatedly making them get up then actually butting them. Must be to do with the hormones but it could lead to the ewe delivering a dead lamb. I would get her out.
Can you get them all into a catching pen? When I was effectively on my own for a year, I worked out a system to catch the whole flock. I set up a hurdle pen in the highest corner of a field (sheep apparently like going uphill for safety) with a swing shut hurdle to close them in, once in. To get them there, I put out one or two 50m electric net fences (not electrified, just there and taut), in a funnel shape. Using my Jack Russell to bark and yip, and me on my 'disabled' off road scoot, I could direct the sheep into the funnel then into the pen and shut the last hurdle behind them. I could have put feed in there but I didn't.
This method worked and I looked after the sheep on my own for a year. I learned after the first go to tie all the hurdles together top and bottom, as a flock of shoving sheep can tip a pen over.
It takes a while to set the whole thing up but it beats trying to chase a pregnant ewe round and round a field