At this point I gave up keeping track and just wanted to know how many 'r's I could add before the search returned zero results: 45 for the singular and 30 for the plural.
|girls, girl||1.25 billion|
|gurls, gurl||19 million|
|gril, grils||6.1 million|
|grrl, grrls||2 million|
|grrrls, grrrl||2.3 million|
|grrrrl, grrrrls||142 thousand|
|grrrrrls, grrrrrl||42 thousand|
|grrrrrrl, grrrrrrls||14.3 thousand|
|grrrrrrrls, grrrrrrrl||1.1 thousand|
|grrrrrrrrls, grrrrrrrrl||2.8 thousand||grrrrrrrrrl, grrrrrrrrrls||under 700|
Clearly there's still uncertainty as to whether two or three will become the standardized version of this slang (though it may be that the two will take on two different shadings, as well, and both remain in place).
update: prompted by elementaryhistoryteacher's comment, I added two lines: "gril, grils" for the most common uncorrected typo (which seems to be deliberate in some cases) and "gurl, gurls" which is by far the most popular variant. Now, someone has to figure out what it means, and that someone isn't me.