Friedsam is a talented young german player and i expect her to become a TOP-50 player at least. Her serve is very good, and unlike most of the WTA players she is quite impressive on her second serve. She also has a strong backhand, whereas her forehand is a bit shaky at times.
She twisted her ankle in december of last season and also received a knee injury during the wimbledon qualies, and that's why her season hadn't been that successful until July. But after that she won two 50ks and a 25k, so at the moment she is an in-form player.
Nonetheless i expect Petra to win, because i still regard her as one of the greatest talents on the WTA tour and under normal circumstances she is the better player.
But given Petra's erratic performances of late, i expect a rather close match, something like 64 75.