My wife won't have sex more than once a week

My wife doesn't have sex with me more than once a week, because a friend of hers told her it that doing it more than once was abnormal. I keep telling her that it's a ridiculous notion, but she can't seem to get the idea out of her head. This is affecting our marriage, but I don't think she gets it. Should we consider counselling?
It's difficult to put a finger on how much sex a person should have. There are two adults involved, so the logical thing to do is have it as many times as you both feel you want it. That's pretty much all that human beings have done on this planet since the dawn of time, after all. Having said that, it's also your wife's prerogative, considering it is an act of intimacy that involves you both. If it's a medical condition that prevents her from being interested, maybe counselling or a therapist could help. If there's no rational explanation for why she feels that way, all you can do is talk to her, try to convince her, or try seeing things from her point of view and learn to live with it.

My girlfriend and I split two months ago after being together for three years. I was devastated, but am finally coming to terms with it. A friend of mine wants me to consider going on a date with a girl he thinks is perfect for me, but I'm nervous because I'm afraid it may end up being a rebound relationship. Should I go?
Getting right back up and moving on works for some people and, as you point out, leads to superficial relationships for others. People go through cycles of grief after a traumatic event, and you're probably just not ready yet. I suggest you give it some time if you're nervous about what might happen. If this friend of yours believes the girl is right for you, chances are she'll still be around when you finally feel ready to take on the world.