If we're going by fluff though, by 'battlefield medic' I imagine they lurk in the army's baggage train and medical tent rather than on the front line of an infantry unit though, and having multiple instantaneous healing abilities sounds more like the realm of battle magic than the slower, less risky ministrations of Shallya.
Plus let's be honest, it's not like the single attack of a wizard is worth very much, and the devotees abilities seem far more valuable than a warrior priests as they cover multiple units: someone nearby needs healing every turn.
How about just limiting the devotees abilities to the unit they are with, rather than within 12"? That would speak more of the personal medical attention that I associate with Shallya than long-range healing magic that sounds more like Lore of Life but without the risks of miscasts. Just in terms of synergy with Bret units, no one minds a 45pt peasant healer picking up peasants standing near her, but when she starts healing multiple Grail Knights with a bound spell, they might wonder why the devotee is better at keeping them in the fight than servants of the lady at twice the price!
Bear in mind that a warrior priest has a page of special rules as they exemplify the Empire, whereas a Devotee of Shallya isn't the same iconic figure for Bretonnia- that should really be a Grail Knight or a Damsel
The devotee might be based on a warrior priest, but the unit they are competing with when choosing a Bret list is a lv.1 damsel with one random spell and one s3 attack at 70pts, so that's why we'd need to make sure both are vîable picks. At 45pts, that list of bound spells and inate abilities is far more attractive. Perhaps we could say that a devotee can only use common magic items, to accentuate that they don't have access to Bret relics?
You also have the devotee both channeling dispel and power dice, just like a wizard. That seems unusual as they don't have spells, why not just dispel dice like a WP?
I'd also be wary of having one of her bound spells increasing her inate unit regen from 5+ to 4+- that seems open to abuse if she joins allied units, granting elite infantry a 4+ unmodified save for 2 combat rounds on a 3+ bound spell. Perhaps start at 6+ and increase to 5+ with a buff.
All in all, I think there are too many unmodified saves involved- I think you are better off choosing the ability that defines them (probably a bound healing spell) and keeping them dirt cheap, rather than have them act as a hybrid unit buff/battle wizard/bound spell caster. Generally it's more enjoyable for both players to have their own abilities in play than focus on blocking enemy damage directly.
It's also a very complex unit for 45 points. If you did have to simplify it down to one ability that defines them, what would you pick? I think even worrying about one miniature being a pacifist in a large scale fantasy battle is too much, as even wizards don't get parry saves with sticks, and it's adding rules to represent the minor fluff where we would want to focus on the major!
I think I'd probably ditch all the path of peace defensive stuff, not because it's a bad idea, but because it's unnecessary as most players do their best to protect casters through good play, not a net of three ward saves. Peasants probably aren't keen on people stabbing damsels either. Similarly, you don't need to say 'no penalty for declining challenge' on a LD 6 wizard
Although it might be amusing to see a desperate Bret character slap a devotee with the Gauntlet of the Duel!
For 45 points, I think channel dispel dice, 3 bound spells (bear in mind in a cavalry-heavy army if she heals 2 knights she's paid for herself) and a 6+ regen on the unit is more than enough in a Bret list compared to a lv. 1damsel for 70. What do you think, if you really had to strip it down? I think we should really aim for something like an Empire Engineer or Witch Hunter- a secondary character with flavour added through a few small special rules, not something so intrinsic to the army as the WP is to the Empire.
I suppose I'm looking at it from the perspective of 'how does this fit within the army of Bretonnia without reducing the appeal of the more iconic Damsels with life magic' and 'is any of this open to abuse', rather than 'is this appropriately costed compared to a warrior priest'.
I do love all of the older warhammer mythology though, I was playing wfrp in the 80s so it all comes flooding back