My Wife's Inner Thigh Is Red And Swollen. It Started

My wife's inner thigh is red and swollen. It started about 2 inches wide and 6 inches long along the length of her leg starting about 4 inches from her crotch. It is now moving down her leg towards her knee so it is now about 8-9 inches long. All this has transpired in four days. Four days ago she woke up in the morning and said that her thigh hurt like she just did a big work out the night before. We were wondering if it was a clock but were told that clots move up the leg not down. Do we rushed her to emergency or just get her in tomorrow morning? What could it be?