I'm sorry to see that no one has responded to your question earlier. Different experts come online at various times; I just came online and saw your question.
Yes, female turtles do lay eggs even if no male is present. While it may be better to wait for an older age to breed turtles, they will lay eggs when they're ready, regardless of age. Egg-laying can be a dangerous event for captive turtles. Your turtle almost certainly has more eggs inside her. She will probably retain them as long as possible while she seeks an appropriate nesting site. This retention can cause infection, organ damage, and even death. Symptoms of a problem may include not laying eggs, laying only a few eggs, lethargy, pacing, lack of appetite, prolapse, digging motions, and kicking of the back legs.
You'll need to provide her with a nesting site as soon as possible. For a slider, that would be a 50/50 mix of sand and organic compost, about 12 inches deep. The bigger the area you can give her, the better. You may have to move her to a preformed pond or a child's wading pool to make room for everything she needs. Be sure that you continue to provide UVB light and a basking light no matter where you put her. This site has very detailed instructions for making nesting sites, including photos:http://www.tortoisetrust.org/articles/Nestsites.htm
At this one, you can read more about egg-laying and egg retention:
Be sure to provide plenty of calcium. You can do that by placing a cuttlebone (sold in bird departments of pet stores) in her water.
If your turtle does not lay more eggs (she may have as many as twenty), that is an indication that she needs help. You'll need to take her to a reptile vet. X-rays will help determine the nature of the problem. The vet will decide whether it's appropriate to try an injection of a hormone that will induce egg-laying, or if surgery is necessary. Here is a directory of reptile vets:
This is a serious situation, so be sure to build a nesting site as soon as possible. If you have further questions, just let me know by clicking on REPLY. I hope the egg-laying will be uneventful.
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