Her default armor provides decent protection and 100% increase in magicka regeneration. Her comments are also misplaced, more often than not. While other mages are fragile, she is tough and has plenty of magicka. Archery Practice: head to Angi's Camp, located southeast of Falkreath. There's a whole range of such quests, and as one would expect there's even two quests for archery. Mjoll standing above bunch of dead bodies saying : "I really missed traveling like this.". Some quests in Skyrim, when completed, will grant you with free training in a specific skill related to the guest giver or to the nature of the quest itself.
Mjoll's comments are misplaced most of the time to the point that I wonder if it was meant to be some kind of joke. Dragon encounter site is good choice, bandit or giant camp, too. One only needs to make sure to fast travel to a place from which Aerin would never return. If one fast travels while Aerin is still talking, there is a good chance that he would fast travel along with Dragonborn and Mjoll. When one is inviting Mjoll to join, Aerin often makes a comment, like "Never seen Mjoll upset like this". If you need to get rid of Aerin, there is a way. Mjoll is tough and her attacks are devastating. Coven of Namira is the only thing that matters to her and she sees Dragonborn only as Namira champion. Other than that, she is, basically, a religious fanatic. Like gear which reduces spell cost, increase magicka, or increase health or stamina.