Probably wouldn't hurt to tell them the truth that we're from a dying military ship that's missing most of it's crew come to see a military base that turned out to be just as much of a ruin as every where else.
We have the resources to survive for six months, give or take. We aren't in a critical rush, so I recommend not being too specific about the state of our current residence. If they think we're residing in a fully equipped military base, they're less likely to try and attack us. I recommend telling this "Mum" character that yes, we did come from space, in an Imperial Navy vessel, and are currently residing in a nearby Imperial Navy base.
We want to establish peaceful relationships with these people, they may be able to provide the resources we need to get back on our feet. I can't think of anything immediate that we could offer them, aside from physical labor and your computer skills, but I'm sure there are some things that the two groups could find reason to exchange. I still recommend avoiding the mention or display of your powers for now, unless absolutely necessary.
I recommend asking them for information about their settlement, if they're willing to offer such information. The more we know, the more informed of decisions we can make about how we can help them, and how they can help us.
If for some reason any of them attacks you, fight to defend yourself and disable, and try to avoid any permanent injuries, and instruct Twitchy to do the same. The last thing we want is blood on our hands. But continue to be wary of them, we don't know what their combat capabilities look like.
Our primary goal here, is to provide a positive first impression to this "Mum", so I encourage you to be respectful and polite in your interactions with her. Answer her questions as honestly as you can, without revealing your powers or your status as a scion of the plague.
Additionally, these people may not be aware of the Plague at all, so telling them that you escaped from the plague might not be a good idea, as it has the potential to incite a panic. Asking the other voices for feedback on this one. If nobody else replies, my recommendation is that you don't mention that your ship came from The Plague.