It all comes down to personal preference. For me I love playing PLO but I make my money NL Holdem. They say that NL Holdem is the Cadillac of Poker and Doyle Brunson even says it's the only pure game left. Just his opinion of course.
If she is only used to 5 card draw and has never played online than I would probably give that a go first but if you are in it for the money than at some point she will have to learn Holdem because that's where the fish are and hence that's where the money is. However in saying that, Holdem is a lot harder for a beginner now than it was when I started in 2002. Just have her look around here and the rest of the web. Memorize starting hand charts first and than move on from there.
There is a ton of information right here at your fingertips. If it's not already here, ask a question in the forums, and I am sure you will get the answer you need.
Good Luck. Hope this helps,
Robert