Once you earn enough points to reach your Pinnacle, Valkyrie will appear before you and ask if you're ready to receive your blessing. Make sure you have enough empty slots and extra weight in your inventory before accepting your blessing. If you decline, you can simply earn more path points, and she should reappear, asking you the same question as before.
"May Odin's favour be upon you!"
After completing the first two chapters, including receiving your Odin's Blessing, talking to Valkyrie will give you the option of being warped to Odin's Armory. If she still doesn't give you the option after completing the two chapters, try to get your character killed then try again. If there's still no access, use @request (See: Reporting Guidelines) and ask a GM to check your Storyline.
Another role she plays is that she is she announcer of Odin's Shower, a GM-triggered event where 100 items are dropped every second in a random map.