What Causes Feeling Faint?

Hi, my mom is taking 20 mgs of lisinopril for her high blood pressure, as she had symptoms of TIA back in January of 2014. On Thursday morning while standing in kitchen preparing lunch all of a sudden out of nowhere she feels like she s going to faint and lays down on the kitchen floor. My dad took her blood pressure and it was not too high or too low. He took her to a walk in clinic and from there she was taken to ER for CAT scan because he thought there may have been some left-sided weakness. Mom stated she began to feel better before she even got to the hospital but then when stands for any length of time she will begin to feel weakness. Like today, could not stand in church. She has been having low blood pressure so doctor said to take half of the lisinopril since her blood pressure has been low. What could be causing her to feel faint when the CAT Scan doesn t show any heart issues. Anemic? Is it okay to take lisinopril and also be anemic? She is scheduled to go in for blood tests next week, but is there something to be aware of about anemia and lisinopril and is there something she could do to help the weak feeling, low blood pressure feeling in the meantime?