Is petunia a witch?

petunia is a not a witch, but a muggle. Her sister Lily is a witch and probably the first one in centuries, I would dare say, in her family. petunia wanted to be a witch, but unfortunately she did not posses any magic and trough her veins didn't run not one single drop of magical power...However she did write to professor Dumbledore in hope he would except her like he did Lily, but we all know that didn't happen, so she stayed uchungu, chungu trough her whole life, hating the memory she fought not to show...