A plastic box filed with soil/sand mix, at least as deep as the length of her shell, placed inside the tank with a ramp or some other means by which she can climb out of the water when she wants, it can double as a basking area. If she is gravid she will lay when she's ready, not when you put her in a box, but she may still consider the box unsuitable and lay in the water.
Putting her out in the garden whatever the weather is not a good idea, she'll feel stressed and vulnerable and will definitely not lay under those conditions, and she may want to visit potential nesting areas several times to decide whether or not they are suitable anyway.
Are the eggs likely to have been fertilised, does she have a mature male in the same tank?
0.2.0 Southern Painted Turtles
0.2.0 Common Musks
1.0.0 Classic Cornsnake "Slim Jim"
0.1.0 Amel/R.Okeetee Cornsnake "Candy"
1.1.0 Phelsuma m. grandis "Desmond & Doris"
0.2.0 Tibetan Spaniels "Ruby & Sapphire"
0.2.0 Brahma Hens
0.1.0 White Silkie Bantam
1.0.0 Belgian Hare "Geyser"
0.0.1 Grammostola pulchra
5.15.3 White Fantail Doves
2.2.0 Indian Runner Ducks