Typically an ovulation is hard to miss if you're lucky enough to be around when it happens..should be a really pronounced swelling. The weight gain is intriguing though. Put in a nice basking spotlight so she can warm up the developing ovum..though it doesn't look like there's room enough in her tank in the pic for a basking area that won't raise the ambients too high overall. You could possibly put heat tape on one side thats good and warm so she can self-thermoregulate. Good luck, this is the most exciting time of the year!
Bill