Well obviously she is breaking UK copyright law. So the question the court will have to answer is whether or not the UK copyright law is in breach of EU law and whether or not when the case is sent back to the UK court, that court should disregard their own national law.
I don't know what the provisions in question of UK copyright law are, but that doesn't really matter. From a EU law perspective the starting point is that according to the European Court of Justice the integration of the internal market has been completed. As a rule, all restrictions on imports and services among EU states are a breach of EU law.
Now the question becomes whether or not that service provided by the Greek satellite broadcaster is legal. Obviously only legally provided services enjoy the protection of EU Law. This is where it gets tricky. On the one hand it is inherent to copyright law that it restricts the choice of suppliers once the copyright is granted and free and open competition is protected by the fact that any company could bid on the right to broadcast Premier League games. From this point of view the service provided by the Greek satellite broadcaster is illegal.
On the other hand I'm sure the European Court of Justice will have a problem with the fact that within the presumed internal market, it's still member state borders that decide which services a European citizen has access to. Exclusive broadcasting rights restrict cross border member state competition within the EU. So what would happen if those exclusive rights became illegal? I don't think it would be that bad for the Premier League. Presumably 27 different satellite broadcasters (as many as there are member states) would offer their services in the UK market. This would make it cheaper for UK citizens to watch the Premier League but wouldn't necessarily decrease the income of the Premier League because they would get more money from the satellite broadcasters in the other member states because they've been given access to a bigger market.
So here's what I hope they decide : It's OK to have copyrights granted in an each member state (basically because the European Court of Justice has no jurisdiction to say anything about that). However that copyright is only exclusive regarding other providers in that member state. "Cross border" supply of services can not be restricted.
This case is being handled in Grand Chamber. Which means there is no clear answer and it takes the combined legal expertise of all the judges to decide and more than likely it will be a decision that either completely upholds the UK provision or severely changes copyright law in all member states. It also means that the decision they reach is as final as can be and can only be theoretically overturned by amending the treaty.