What does it mean for a stroke to peak? my mom had a stroke 3 days ago and we thought she had another but the doc said it had just peaked

Stroke evolves: It may take several days or even weeks for the full extent of the damage caused by the stroke to be completely expressed.

Swelling : After a stroke, there is the natural process of swelling(edema) around the area of the stroke. This tends to get worse before it gets better and the symptoms reflect this. When one refers to the stroke "peaking", one is usually referring to the maximal swelling occurring then hopefully going down.