Can a girl get pregnant if you pre-cum on her and then wipe it off with a tissue, and continue fingering her with the same hand that you wipe with?

Technically speaking, it is theoretically possible...
although not probable...

If there was sperm on your finger, when you inserted inside her, and it was pushed up to her cervix, it could have swam up further, and found it's way to an egg, if she had ovulated recently

It's less likely to occur if your partner ejaculates outside of your vagina. But it is not impossible. All the little buggers needs is a warm wet environment, and who knows what they can accomplish. The fluid that comes out of the penis before ejaculation, is pre- ejaculate. It can contain sperm, and therefore it is possible to get pregnant even if the man withdraws before he ejaculates.

Now, sperm can live inside of a woman's body for two to five days, or up to a week if they reach the fallopian tubes. A woman's reproductive tract is hostile territory for sperm. The pH of the vagina kills off most of them, and of the one percent that make it past the mucus plug at the bottom of the cervix, most end up in the wrong tube. Given the vagina's apparent hostility towards the sperm, and the sperm's poor sense of direction – it seems like getting pregnant is a difficult thing to do. But the one million unplanned teen pregnancies and 1.5 million abortions that go on in the US every year suggest otherwise. A couple having unprotected sex for a year have an 85 to 90 percent chance of getting pregnant. After all, the egg, is about 85,000 times bigger than the sperm cell. It's not that hard to spot.

A woman usually releases one egg a month from her ovaries into the fallopian tube. The release of a mature egg occurs about 14 days before the start of her menstrual cycle. The first day of a woman's period is considered the first day of her cycle. The egg has to be fertilized within 24 to 48 hours of release. Fertilization takes place in the fallopian tubes. Of the 500 million sperm that are ejaculated, about 250 make it to this point, but the fallopian tubes are a much more scenic and inviting territory for the sperm. They can hang around for up to a week just waiting for that egg.

Good luck!