If she saw another child - or even adult - cry, she was pretty much guaranteed to be found hugging them within 10 seconds, as king what's wrong and doing her best to help.
Mere days after arriving at Signal, during the first live exercise she took part in, one of her fellow students injured themselves rather severely, blood escaping the wound at a dangerous rate. Doing, as usual, all she could to help, Helena ran to the boy and pressed both hands on the gash, wishing for the bleeding to stop. Which it did. About thirty seconds later, when the nurses arrived on the scene and asked that she remove her hands so that they could evaluate the damage, the bleeding had completely stopped. Helena had just used her semblance for the first time.
Since she'd been practicing archery since a young age, however, they would probably end up being secondary.
Her semblance is, in one word, Life. It allows her to use her Aura to do a few things.
2) Grow plants. Plants grown this way will not sprout new flowers, or have their flowers bloom, because of the artificial growth, although it will happen normally afterwards. As a general rule of thumb (with trees, for example), 1% = 1 year growth equivalent, although smaller plants like moss grow more easily.
Artemis takes the form of a large, reflex flatbow and its 24 (25 if you count the special one) accompanying arrows, along with a quiver.
A single arrow, held onto the quiver to be separated from the others, only has a bodkin point, but this one point is made of hyperdiamond.
Helena had Artemis custom-made for her while she was at Signal by a company called Prometheus Labs.
Shi: A lethal toxin that blocks oxygen processing within mitochondria. Effects start immediatly and death usually occurs in about 10 seconds. This can still be reversed for approximately 4 minutes by injecting the antidote directly into the heart.
THE TOXINS ARE INEFFECTIVE IF SOMEONE'S AURA IS UP.