Hi, I'd like to help you with your question.
The fact that you are concerned enough to bring this topic up with your wife says a lot about how her drinking is affecting you, if not her at this point.
There are two points that are problematic in this situation. One, you are concerned about her drinking and she is not listening to you. Either she is an alcoholic and is in denial, or she isn't concerned with your feelings on her alcohol use or in any other situation in your relationship. If you see signs that other concerns you have in the relationship are being ignored, this needs addressed. If you wife is in denial, this is a sign she is an alcoholic and does not want to face the consequences of her use.
Two, the fact that you feel she has worked her way up to 4 to 7 beers. Someone who is increasing their use of alcohol is in danger of alcohol abuse or addiction.
If your wife refuses to get help, you can still work on this issue. Contact Al Non at http://www.al-anon.alateen.org/ for ways you can help yourself and your wife. They can help you work on your feelings about her drinking and also help you determine if she may have an alcohol problem.
Denial is a very difficult thing to work through. If your wife is alcoholic, then there are ways you can help her. Intervention is one. Getting support for yourself is another.
Here are some books that can help you. One is called How Al-Anon Works for Families & Friends of Alcoholics by Al-Anon Family Groups. Another is Addict In The Family: Stories of Loss, Hope, and Recovery. by Beverly Conyers. You can find these on Amazon.com or your local library may have them available.
I hope this has helped you,