I find it very distasteful reading what many of you have written on this thread. I can only assume some of the embarrassingly juvenile responses were written by school boys.
A womans vagina can stretch open enough to expel a baby, so three fingers is no test whatsoever. i think you are confusing what you percieve to be a virgins mentality with that of a virgins anatomy. its is true that the hymen will sometimes restrict insertion, however most young girls are using tampons by the time their 15 or so and that in itself can cause the hymen to break, or at least stretch readily. That with things such as horse riding, gymnastics etc means that by the time sex is on the agenda the hymen is often no longer a problem.
I would also like to add that instead of seeing this 'looseness' as you call it as a negative thing, you should see it as an indication she felt comfortable enough with you to relax and be fully turned on. when this happens the vagina becomes lubricated and naturally loosens allowing for penetration, this is a good thing!!
Finally i imagine that you are confusing the visable looseness of the vagina with the natural size of her labia. As unless you have opened her legs wide and peered up her, you wouldn't be able to judge the size of the opening. What yr more likely seeing is the skin folds of the labia that in some women are large and can look 'loose'.