My 89 year old mother fell and they are saying she has a slight dislocation of pelvis, is this possible or am i hearing the doctor wrong?

Likely stable: Elderly individuals that sustain low-energy falls can have pelvic ring injuries with pubic rami fractures and impaction fractures of the sacrum. I doubt she has a dislocation, those typically are associated with higher energy injuries. The rami fractures are stable and she can walk on it safely without displacing if there is not a complete sacral fracture.