The purpose of the I-130 is to establish the relationship between the petitioner and the beneficiary. When an I-130 is approved then your daughter will be eligible for a greencard when one becomes available in her category. She is in the family category 2B , depending on what country she is from, a visa won't be available for 5-11 years. If she gets married during that time she will lose that priority date and you will have to file again. If you naturalize she will be in Family Category 1 which will be faster, so you should naturalize as soon as possible and her category will be upgraded. Also if you naturalize and she marrys before the greencard is available she will not lose her priority date, she will just move to category 3. THere is no category for married daughter of greencard holder but there is for married daughter of U.S. Citizens. You can find out what priority date's they are processing for each category by looking at the visa bulletin. The dates change each month. This is the most recent. http://travel.state.gov/visa/bulletin/bulletin_5212.html
It will be a long wait. YOu should speak to an immigration attorney about naturalizing so that you can help speed up the process for your daughter.
Andre Olivie, Esq.
U.S. Immigration Lawyer
206 724 1940