considering she's available only as 4-5*, I think a 5* merge might be better especially since you invested so much into her skill wise. Building up a 5* merge will take a while simply because of the feather requirement which should give you plenty of time to slowly summon more of her.
Btw if you're going to use swift sparrow on her you might consider +spd on her. It'll bump her up to 29 base speed, with buffs and SS she'll go up to 37 speed.
If thats not enough speed probably go with darting blow to get get her speed up to 39. Focusing on trying to double with blade tome damage, because you're more likely to kill things with 2 blade tome hits rather just stacking a bit of attack when blade tome damage gets so high with buffs.
That's all assuming unmerged stats at 5*. With merging her speed will increase up to 4 points more.
Otherwise if not going +spd, a raven tome build might be better so she's not so buff dependent, but still dishes out a lot of damage.