When deciding on what to do, I find it helpful to remember that the rumen is barely functional until 6 weeks old, so they can't really sustain themselves without milk until then. It's fully functional at 8 weeks.
They will do better on mum's milk, and if they aren't feeding from her then you will need to dry her off, which can be tricky at this time of year. And she will need a friend, so then someone else has to be in and on straw with hay, too. So unless the ewe is really hating it, I would carry on with the twice a day lambs feeding off her, and, yes get some pain relief into her in case her reticence is pain-related. You may find she settles back into suckling after a few more days, otherwise you will still have the drying off issue whenever you decide to stop letting the lambs feed - unless you send her straight to slaughter once you take them off her.