Well... that's not through the heart, it's through the bottom of the sternum. The heart is off-center, not smack in the middle of your chest. She nicked it, and for a Servant that might not be enough to count as destroying it.
No, Bryn's spear is large enough to cut through his heart even with an aim like that. Gotta hand it to Sigurd's Runes tho. He regenerated rather quick