do NOT buy anything over the internet. you have no idea what you're doing and will buy something junky that doesnt fit your wife and that neither of you know how to assemble safely.
first, ask your wife if she really wants a new bike or is content riding what she has. if she wants new, have HER go to a local bike shop and tell them what she is after. you stay home so you dont get in the way and obfuscate the decision making process.