Okay, here's what happens after we leave Ravi ...
When the Mayflower enters normal space to drop a communications buoy, they detect a signal with an Alliance signature coming from the surface of a nearby planet. They soon conclude that it's the Swiftsure. There is much debate about what to do and much argument over what this means for the future of the Mayflower -- 1) There is no Elpis colony for them to go to, 2) Why the cover up?, 3) Should they turn back 7 years into their mission?, 4) Should they even bother to find out what happened to the Swiftsure? The planet the ship is beached on is hostile and barren. They send a team comprised of command-crew members and two of the ship's robots. They find the Swiftsure wrecked on the planet and it's computer -- Oracle -- damaged but perhaps repairable. And then the crew are attacked by two infected members of the Swiftsure.
They bring the infected aboard along with those injured in the attack. What they don't know is that the cause of the infection is an airborne virus -- a virus originally engineered to cut-and-paste the DNA of the colonists in preparation for life on Elpis. What's happened? Did the environment of the planet cause the virus to mutate and evolve? Or is it something more sinister?
Yep, something more sinister. Sabotage! Someone prevented the Swiftsure from completing its mission. And the same thing that happened on the Swiftsure is happening on the Mayflower. People are becoming infected and becoming mindless, blood-thirsty zombies.
At the end of the tale, the crew of the Mayflower make it to Elpis. And in a bid to save themselves, the surviving command crew dumps the entire section of the ship containing the colonists on the planet and makes a run for earth. (This explains why Steve's story mentioned that the Mayflower crashed on Elpis and why the Elpins aren't fans of Earth people). But before they complete the separation, one of the people left behind makes sure that the drive section of the Mayflower doesn't make it back to Earth.
Fast-forward to Sally's story ... (and all this is a big MAYBE) ...
The Mayflower crashes on Mars. It's believed to be just space junk, but the Martians find survivors -- all in hibernation. (But they don't know anything about the ship -- what it's called, where it came from, who is on it). The Martians soon discover that there's something wrong with the survivors. Maybe that's why they send Sally's main characters to further investigate. Maybe someone is thinking of weaponizing the virus. Maybe someone knows that they're sending Sally's characters to a deathtrap.
Then all this should somehow bring my main character into contact with the crew of the Speedwell.