Is it obligatory to perform ablution for every prayer and to wash undergarments if drops of blood are released from the anus occasionally due to hemorrhoids?

If the bleeding is constant most of the time, then she is considered to have a perpetual impurity (sahibat hadath da'im), and she should perform Wudu for each prayer when its time begins. If it is not constant, then she is not considered to have a perpetual impurity. She is not obligated to wash off any blood that gets on her clothes, as a concession to ease hardship and remove difficulty.