You've gotten good advice to let Waddles keep her eggs for about 3 weeks, and to ensure she's got food and water close to her "nest." I'd like to add just a couple of things. It's not easy to give many of our birds unfiltered sunlight. If you're in a climate where the daytime temp is lower than 70 degrees these days, you don't want to set her cage outside or beside an open window. Here's what renowned vet Margaret Wissman says on this subject:
Healthy Birds Consuming a Pelleted Diet Should Not Require Sunshine (Unfiltered By Glass or Plastic) for Their Vitamin D. Don't get me wrong. Sunshine is very good for birds, and if possible, pet birds should receive sunlight, not filtered through glass or plastic (which filters out the ultraviolet rays), an hour a week during the summer months, and perhaps an hour a month during the winter.
The uropygeal gland (also called the preen gland) secretes an oily substance that the bird spreads over the feathers. This secretion aids in waterproofing the feathers and helps keep them supple. The secretion also has precursors of vitamin D that are spread on the feathers during preening. When the bird's feathers are exposed to natural sunlight (or full-spectrum indoor lighting), the secretion is changed to the active form of vitamin D, which is then ingested when the bird preens. Vitamin D is necessary for a bird to properly utilize calcium, which is necessary for strong bones, normal eggshells, muscle contractility and more. However, if a bird is eating pellets, vitamin D is added to them, so providing a bird with sunlight shouldn't be necessary. (This excerpt is item 16 in the list at this link:
http://www.exoticpetvet.net/avian/20facts.html )
I'm curious why you don't let your 2 tiels be together. I think keeping them separated has a MUCH greater chance of causing depression for both birds than your preventing eggs from hatching ever would. Tiels NEED a partner IMO. Even a same-sex partner is much better than being alone, especially with another tiel close-by but separated. It's so easy to gently boil fertilized eggs to ensure they won't hatch. I hope you'll give this some thought as you're watching over Waddles so closely these next few weeks.
Good luck to her!