The brown discharge was likely a little damage to her cervix, which can be sensitive. She can't get pregnant that way - although technically it just takes one sperm, the sperm also needs seminal fluid to swim around in and neutralize her body's PH, which will kill it without seminal fluid. Best wishes.
I don't think it can be so easy to be pregnant-you finger isn't deep enough and the Sperm can easily die in the air.The water can really wash out almost of your sperm.If you are still worring about this,you can buy a pregnancy test kit.It's not very expensive-maybe you can buy it.
At this point, a pregnancy test would be accurate. She could get one cheap at CVS, Walgreens, Walmart, etc. It's highly unlikely that she would be pregnant.