Hi Chip,
I think it's great that you want to do the right thing to protect your cat. You can most certainly keep her indoors. We have two cats and have trained them to stay indoors because we live on a very busy road where people tend to speed. We keep our cats in for safety reasons.
A couple of things I'd recommend to make her transition to being an indoor cat more "interesting" for her...
Get her a window seat or two, if you don't have wide windowsills that she can nap on.
Something like this:
Make sure she has a good litter box and that it's kept clean - sometimes cats prefer the outside because they're very picky about their bathroom. Keeping her bathroom facilities clean is important.
Is she allowed in the basement or garage? Cats love to roam and "hunt" having a place she can prowl will help.
I also assume that she's been spayed - if not, then that would be wise. Un-neutered pets will have more of an "urge" to go outside and roam than neutered pets.
Finally, call her vet's office and ask their advice as well on what you can do. There's generally office staff or vet techs who would gladly help you to keep her safe.