I've got no problem with her being capable (I've wished nothing more for the character for ages), but she clearly wasn't. And since she wasn't she had no place being there.
No... In this particular battle it was Medusa who wasn't capable. Her mistake is what led to Jen's injury. And the potential of casualties shouldn't prevent someone from taking part in a mission.
Jen was on the team that took on the Greek Pantheon. She has stood up to the Champion. I feel that her record clearly shows that she was a good fit for the mission. It went sideways and she paid the price but that doesn't mean she shouldn't have been a part of the team.
What I didn't like is her statement at the end of the issue when she told CM to fight to change the future - doesn't that go completely against what she was saying in the 0 issue?