In those circumstances I would lay off the drugs for now, but monitor carefully.
It is your choice if you choose to breed from her again, as you are clear about the potential implications. I have a Kerry Hill ewe who is one sided (since last lambing time), she is a super sheep and I did breed from her this year, she can raise one lamb no problem, had she had twins I would have topped one up and lifted it as soon as I had a sheep to set it on to, I do this because I love the sheep and I lamb the Kerrys earlier than everything else so I do have the time to deal with twins from her if need be, but I wouldn't keep a one sided sheep in the commercial flock as at main lambing time we wouldn't have time to deal with it, and the cost implications are high(compared to value) if you end up bottling.