"hi um i was rewatching the impossible astronaut/ the wedding of river song, and i was just wondering what are your thoughts on why river started shooting at her younger self in the astronaut suit if she knew that the doctor wasn’t really dead? then when she runs out of bullets she says "of course not." what do you think that means?"
First of all, some rambling about continuity and timelines: There are two version of events with regards to the happenings of The Impossible Astronaut/The Wedding of River Song. In fact, in TWoRS, even before River and the Doctor touch and time starts again, the second version of events already exists.
Doctor: “Time’s gone wrong. Do you remember why?”
Amy: “The lakeside.”
Doctor: “Lake Silencio, Utah. I died.”
Amy: “But then you didn’t. See, I remember it twice, different ways.”
Doctor: “Two different versions of the same event, both happening in the same moment.”
There remain major issues with Amy’s recollection of the events all the way through to the finale. They are invited to the Doctor’s death, they supposedly witness it, they go on and have adventures with a younger version of him.
But Amy only remembers the second version of events much later, after the Doctor drops Rory and her off in The God Complex. When she meets River in the garden at the end of The Wedding of River Song, it is there where she begins to cope with most likely never seeing the Doctor again and her actions in the aborted timeline.
River: “I just climbed out of the Byzantium. You were there. So young. Didn’t have a clue who I was. You’re funny like that. Where are you?”
Amy: “The Doctor’s dead.”
River: “How are you doing?”
Amy: “How do you think?”
River: “Well, I don’t know unless you tell me.”
Amy: “I killed someone. Madame Kovarian, in cold blood.”
Similarly, the Amy Pond we met throughout the episode, who was leading the team against the Silence, already remembered the events of AGMGtW. Unlike TIA!Amy she knew that River Song was her daughter.
Doctor: “Melody Pond, your daughter. I hope you’re both proud.”
Rory: “I’m not sure I completely understand.”
Amy: “We got married and had a kid and that’s her.”
All this underlines that there never was just one timeline, in which River broke time, in which the Doctor and River married, in which the Doctor shared the secret of his survival with her, right there, during the wedding on top of the pyramid. From the very beginning on, there was a version of events where that didn’t take place.
The second part of series 6 focuses on the events from the Doctor’s point of view - we see him finding out about his impending death in Let’s Kill Hitler and get a glimpse or two of him running from the events at Lake Silencio. This is a Doctor who finally, in a last desperate moment, after already writing the invitations to his own death, found a solution.
But not only that - it is also the only time where we experience a proper sequence of events for River Song. “Let’s Kill Hitler” ⇨ “Closing Time” ⇨ “The Wedding of River Song” represent River Song’s entire early history. We see a River who starts to claim the name for herself in Let’s Kill Hitler, who sacrifices all of her regenerations to save the Doctor’s life after almost killing him, who studies Archaeology in order to be able to make up her own mind. We see her being taken hostage by the Silence again. And then we see her in that ultimate act of rebellion that is “The Wedding of River Song” - not even bowing down the laws of time, loving a man she was raised to hate.
And that is the progression of events which lead us to Amy Pond sitting in her garden, pondering whether she did or did not commit a murder.
Well, but now, after this (totally brief and really relevant) exposition, let’s address your actual question.