The patient who was pregnant was possibly alloimmunised by her foetus to provide non 'D' Rh antibodies. Though the 'D' antigen is the most potent in production of anti 'D' antibodies i.e. most immunogenic, followed by anti 'C' and anti 'E' which was responsible for the incompatibility of Rh 'D' positive blood. What you have detected are possibly the anti C or anti E antibodies. These need to be checked for as they are usually igG, may cross the placental barrier. The pregnant lady needs to have the antibody identification and the evaluation and more careful monitoring of the foetus.
