Hi, thanks for the photos, I`m as sure as I can be you have a female, and at the current size most likely to be sexually mature.
Have you ever noticed a relatively sudden weight gain?
Edit: As far as the missing tailtip`s concerned, there are normally 10 to 12 black bands, in mine there were 10, the same number in white, I expect there`s around 15cm or so (6 inches) missing in your monitor meaning her "real" current length would be around 120cm (4 feet).
http://farm8.staticflickr.com/7228/6...e5e5a763_z.jpg
As you can see, the head in my male is much more "boxlike" in profile, though we need to keep in mind he was around 12 years old in this pic and it gets more robust with age.
http://farm8.staticflickr.com/7147/6...58ff780b_z.jpg