What am I? [summary of past events, then bare bones dialog only exchange] (Zombie Apocalypse)

Notes and context up front:

So I have this forming idea for a complex zombie apocalypse setting with many protagonists whose paths cross at various times and places and . . . stuff.  This is a world that isn't the same as my pre-existing zombie fics, it probably will include someone on crutches as one of the protagonists.

As I mentioned at one point elsewhere, I totally get the desire to have a cute redhead with freckles in her early teens in your zombie apocalypse fiction, and the older character here, currently just called "Older", is my shot at that.

The younger character, currently just called "Younger", I don't have demographics worked out for at all.  She's a trans girl.  When she was orphaned in the earlier days of the zombie apocalypse she realized that no one was there to force her to pretend to be a boy.  She met her first companion at a pharmacy where the pharmacist was doing the difficult task of staying open until there were no drugs left to give out to those that needed them.

The pharmacist, not an actual doctor, worked out her treatment plan.

The companion met was an college age cis male who showed up to get as many depression meds as possible so that the inevitable return to deep depression could be put off.

Younger was on hormones by the time companion switch happened.  What happened is that Younger and original companion could see that bad people were flanking Older, and would kill her, but only Younger could make the climb necessary to reach Older first and warn her.  Original companion was able to lead some of the bad people away allowing Younger and Older to escape together, but as they fled in a different direction from original companion, they never met back up with original companion.

At this time Younger passed as cis, and never mentioned being trans.  Older knew that younger needs to loot pharmacies to keep medicate, and knew that whatever younger gets there isn't something most looters take, but was unaware that Younger was trans until traumatic event that comes right before the exchange below.

I haven't figured out what it is, though.  I definitely don't want it to be a rape attempt, but whatever it is leaves younger exposed at least from the waist down.  Actually, thinking about it, maybe the people who captured Younger just routinely confiscate prisoners clothes as part of prisoner processing, the better to make sure that there are no hidden weapons or tools.

Anyway, Older comes to the rescue, and the two together fight off the people responsible for traumatic event, Younger gets re-clothed, and the two leave.  Older is left concerned, and the conversation starts when Older is absolutely sure they're in a safe place.

* * *

Older: "Are you alright?"

Younger: "I'm not injured."

Older: "That's not what I meant."

Younger: "Oh."

Older: "You didn't defend yourself at all, you only started fighting when I was in danger."

Younger: "Uh huh."

Older: "What's wrong?"

Younger: "I just--" *turns away*  "It's . . ." *leans on wall* "They're right." *slides down wall*

Older: "About what?  They tried to kill us."

*Younger hugs knees into chest*

Younger: "I'm a freak."

*Older crouches down to look Younger in the eyes*

Older: "You're not a freak."

Younger: "Then what am I!?"

Older: "You're my sister."

*Younger awkwardly lunges forward and hugs Older*