To be honest, it's doubtful that they were hacking. Miss Fortune is an 'AD carry,' in other words she'll do a ton of damage, but be really squishy. She also had lifesteal, meaning every attack was healing her for a % of the damage she dealt, of which due to her gold lead, she was doing a lot.
She had almost twice as much gold as you, and you had the most gold on your team; she had almost 3x the gold that others had.
This is actually something you see happen a lot more often when the players are less skilled, as League of Legends can be a very snowbally game. Most teams of newer players have trouble focusing down a priority target; had you been able to group up and kill her while she was stunned (between Ashe, Pantheon, Jax, and Skarner, you could have kept her locked down for quit a while if needed), you should have had much less trouble with the rest of her team. Unfortunately, 'focus fire' (making a collaborative effort to take out one target first before moving on to the rest) is a skill that doesn't just come out of the blue, you need to work on it.
That isn't to say you can't contact support and ask them to look into it, rather that you shouldn't go into it with the attitude that they 'must' have been hacking.
TL;DR: A player getting a large enough lead early tends to do especially well in earlier games, for a variety of reasons.