Unless the Colly managed to make a precision jump, very close to an outbound node, I doubt she ever would have been able to leave the system before it went nova, due to how slow she is in first place and due to the heavy damage she took from the Shivans.
hand waved because it depends on how fast the colly can recharge her jump drive, which is vague concept in FS only mentioned and loosely employed in kings gambit, but I would be extremely surprised if it was more than a few minutes per jump, more than enough time to make a crude escape jump away from the GD node, calculate a precise jump to its evac position, before escaping the system. Given the ships size, importance, crew size and damage level, perhaps even loaded with wounded between jumps to help with the evac, it will probably be given priority departure at the node.
Note in the time between the colly's destruction and the sun going nova Alpha jumps back to the Aquitane, lands, climbs out of their fighters, briefed on the Bastion situation, climb into fresh fighters which have to be armed between the briefing and their scramble because the player can determine their loadout before the mission start, scramble, jump to the Bastion, deal with that drawn out ordeal before jumping to the Vega node and spend ages there fending off over excited shivan fighters, bombers and cruisers.
You know, that would've been a decent addition to the FS2 ending, which is, thematically, about humanity's insignificance: escorting the crippled Colossus out of the system, inching towards the node...
...and then losing the Colossus when Capella went supernova because **** you
an interesting perspective, i like where that is heading.