well if she wants to do it at home, the best way is to get a quality hair straightener. This is the one thing you don't want to get cheap, as it can seriously damage your hair if you do. Make sure it has ceramic plates, this protects the hair. I use Solia, but Chi is also a great brand (not sure if you can find them here, but you can find them online.

Before straightening, get a heat protector spray and spray throughout the hair. Dry the hair, then run the straightener through the hair small pieces at a time. Depending on your wife's hair type, it can take a few minutes, or longer. Check out youtube for videos on how to use a hair straightener if she is unsure.

Most important, get a quality straightener. I have used cheaper ones and after about a month the hair is dry and coarse. Solia is the best brand, and although expensive, I have had mine for two years and it has been well worth it.