This is Cowppers gland fluid which is lubricating fluid from peri urethraĺ glands which gets secreted on sexual stimulation. This is Nature s way of preparing you for pleasure by taking away dryness which otherwise would result in pain when you would have subsequently indulged in masturbation or intercourse. So just take things on stride. With GF the intensity of sexual arousal is much more higher. Somebindividualsnlike you tend to over lubricate.

It's a normal sexual response ......whenever u meet your girlfriend u feel sexually excited and due to it liquid from your penis comes out.