It's an interesting opening. There's lots of tension and intrigue. I'm not sure if I'm I like the opening line, but not sure what could be changed, it just doesn't flow right to me. It ends quite suddenly and I'd like to know more. Especially about the central characters dual hearts that adds an unexpected twist. I've just highlighted some things I was drawn to as I read through. Green are just words I feel stunt the flow of the piece a bit, they seem a bit cumbersome, but then I tend to like things simple. I also noticed a couple of slight tense oddities i.e. in your last paragraph 'was' is past but 'is' is present. I'm not very good at tense though myself.

Hope this helps.

"How do you cope with something like that? Constantly on the edge, never knowing, always hoping, praying, wishing… Left in the dark with no way out; where do you turn to, who do you go to? What do you do when one false tip leads to another and the days transpire into weeks, months? At what point do you give up hope, when do you coincide with defeat?

“We still haven’t given up yet. I feel that she is still out there somewhere, alive,” the old lady spoke slowly, her voice strained, her pruned lips barely parting.

“Why do you still believe that your granddaughter is still alive when all evidence points contrary?” the callous reporter asked, their eyes alive with curiosity. I'd prefer to be shown the writer is callous before they speak, rather than being told it after. As I didn't know who was speaking I gave them a voice of my own choosing, to then find out it they are a callous reporter makes me have to go back and re-read a bit with this new knowledge. Same sort of thing happens when the old lady starts speaking, but I can live with that one. They moved their logoed Not sure logoed is a word, try describing it instead. microphone closer to their victim’s face.

The old lady closed her eyes; the lids were as wrinkled as the surrounding drooping skin of her face. She gave a shuddering breath before speaking again. “I would know if my Alexis had… died. Something—my heart—would tell me when that has happened. I know she’s still alive, and we will not stop the search until she is found.” Though her voice was frail from old age, she spoke with a pronounced certainty, as if she was stating some kind of universal truth.

Was that her light, her strength?

I couldn’t understand her loosely based reasoning. How could you rely on mere instinct alone? Maybe there was something wrong with me, something wrong with my heart. Would I be able to know if someone close to me—a person I knew and loved—had died, or would my hearts? continue to pulse its steady, unaltered rhythm.

I held my breath and listened closely to the beats of my hearts, to the thumps of my pulse in my throat, my wrist. The pulsations were steady, and that worried me. My hearts began to accelerate from the fear that something was wrong with its genetic makeup. The character has multiple hearts? If so I think their should replace its, might help to give a bit of background before starting on the plural, my brain started doing that thing where it ignores something it thinks shouldn't be there, like when when two words are repeated.
I opened my mouth and resumed my breathing, taking in a long gulp of air. No, I didn’t understand, I couldn’t comprehend the old lady’s reasoning. The news reporters—as unfeeling and uncaring as they were—were right. Alexis Young was dead.
Did that make me as horrible a person as they were?
With a shudder, I brought my attention back to the still-commencing interview on the small television set. But because my luck was as good as it is, the scene switched from the homelike setting with the news reporter and the old lady sitting unnaturally close to each other( the reporter had inched nearer and nearer in conjunction with her fiendish curiosity) to the business like setting of a news room."