If I ejaculated on my hand, then wiped it off with toilet paper or on other skin, and then fingered my girlfriend could she be pregnant?

Getting pregnant. While it only takes one of your soldiers to find his target the odds if well wiped is unlikely. However, one can become pregnant with penetration even without ejaculation due to the few sperm that may be in the pre ejaculate expressed early on.
We weren't there. You cannot possibly expect a 100% accurate reassurance in this scenario. Here are the facts you have to live by. If there was any fresh, wet, semen on your finger and your girlfriend was ovulating then yes, pregnancy is possible. If she was not ovulating pregnancy is not possible. If there was no fresh, wet semen on your hand pregnancy is not possible.