Although most bars in the Chueca area are quite mixed, there are a few dedicated bars for girls in Madrid. Your best place to start would be Fulanitadetal which is probably one of the most popular....

Truco (Trick in English) is also very popular. Definitely more girly than butch, the music is excellent and the clientele are quite mixed. The staff are very friendly, although it does help to speak a little Spanish. There are several themed party nights which take place throughout the year. Your best bet is to check out the free sheets or ask at one of the bars listed, as they change regularly.