Yes, there were many women in the GULag camp system. Exact ratios are not something that can be easily found for the system as a whole, as there is a tremendous amount of regional archival work still to be done, though it would seem that women were more likely to be sent to the Kazakh agricultural camps rather than to the heavy industry and mining of the Arctic camps, thought there were women throughout the system.

From the end of 1941 until mid-1943 the ratio of females to males would have increased, as those who were guilty of criminal rather than political offences were often given a reprieve to join the Red Army, as many as 750,000 men were released into the various branches of the armed forces. Furthermore the camps were given the lowest priority (with some exceptions for vital war industries) for food and supplies which led to a famine within the camp system and at least 300,000 additional deaths, as it was the men who were most often (but not exclusively) assigned to the most labour intensive jobs, they tended to suffer more in this 'famine of distribution', increasing the female:male ratio further.

If you are looking for more qualitative sources, 'Til my tale is told' an edited collection of female prisoners memoirs and interviews, by Simeon Vilensky is a good place to start.

If you have a specific year/period in the Stalinist era you want more detailed info on I can point you to the right sources to look, as the nature of repression and who were the victims changed significantly between 1928-1953

While I can't speak to an exact male female ratio on those affected by Stalin's purges, I can definitively say that women did end up in labour camps. I highly recommend you check out Eugenia Semyonovna Ginzburg's Journey into the Whirlwind (1967) which is a first hand memoir of her experience as a political prisoner and in the Gulag system. Her detailed account obviously could not be published in the USSR, so it was smuggled out and published in Milan. One of the most enthralling books I read during the course of my undergraduate.

According to one of the earlier post-Soviet papers on this topic [1], the percentage of woman in the labour camps and colonies (excluding places of special settlement) was rose from 5.9 - 8.1% from 1934-40. This percentage rose sharply (peaking at 24% in 1945) as many male inmates were released into the army or otherwise perished. By 1948, when my series runs out, 19% of inmates were women.

This comes with the obvious disclaimer regarding the accuracy of Soviet statistics. It provides a baseline and trend rather than an entire snapshot. So don't put too much in store by exact percentages.

[1] See Getty, Rittersporn and Zemskov, (1993), Victims of the Soviet Penal System in the Pre-War Years. There was another, more detailed 1990 study of this by Zemskov that's worth reading but, annoyingly, I seem to have lost my translated copy.