I think that Clare would be able to. Since she isn't half yoma, but a third, she has a higher chance of getting pregnant than the average warrior would. In the manga, dragon-kin are probably able to reproduce anyway. That would mean yoma are able to reproduce but probably don't because of lack of necessity.
(Dragon-kin are the beings that the organization used to turn humans into yoma. Yoma, as you know, are the beings used to make the warriors in the organization.)
Honestly, even if she was an average warrior, I think she would. Warriors tend not to have relationships because of the way humans see them and the only men they would encounter are Male awakened beings aside from bandits; as we saw with Teresa. They also have a lot of mental illness and emotional trauma; Ophelia for example as well as Priscilla. They tend to be unemotional or so emotionally unstable that it can be very difficult to form relationships at all.
Let's also not forget that they have a large "wound" running from their neck to their groin and might not be able to even carry one without literally splitting in half. Clare's was momentarily closed when she entered The Destroyer but she had to be practically sewn back together when it appeared again.
So the real problem isn't if she can get pregnant, its if she can carry a baby long term without having real issues.