No, your Uninsured Motorist would not cover everything if your girlfriend had an accident in your vehicle.

Uninsured Motorist (UMBI) is normally for bodily injuries sustained when an uninsured motorist is at-fault and crashes into you. There is also Uninsured Motorist Property Damage (UMPD) that covers some of your damages if you are hit by an uninsured driver.

Your UMBI and/or UMPD would not cover an accident that your girlfriend was at fault for since this coverage is for someone doing damage to you not you or another driver in your car doing damage to others.

Instead if your girlfriend, or anyone else, drives your vehicle you need to read through your policy and check with your insurance agent to see if they will be covered by your policy. Liability covers damages done to others by the driver of your vehicle and Collision would cover damages done to your own vehicle so you would want to make sure these coverages extend to your girlfriend or anyone else that operates your vehicle with your permission.

If your girlfriend does not have insurance of her own than it is still okay in most states for her to drive your car as long as your policy covers her when she operates your vehicle. Even if she did have her own insurance policy it would be your insurance as the car owner that would be primary and her insurance as the driver that would be secondary and used only if your limits were exceeded.

So if your girlfriend has had an accident in your vehicle already contact your insurance company to make sure your coverage extends to her and to see about any claims that need to be made. If she has not had an accident but you are just concerned about what coverages you have that extend to her as a driver than check with your agent to make sure she is covered by your policy's various coverages.