She's laid about 5-6 clutches in her lifetime, and they had gotten smaller every time. Is she just old? She seems more inactive now, too, and doesnt mate nearly as often as she used to.
What else is in the tank- is this a community tank? If it's just the snails- you may want to consider a buffering substrate to raise that pH and GH. Depending on what else you have this might or might not be smart.
Also consider adding some crushed coral to your filter... or... add a little baking soda (just a little mind you) to your water in a water change- I have naturally acidic and very soft water and add 1/2 tsp per 5 gallons when doing water changes.