1) That's a fascinating question that I've never seen discussed in occult or spiritual literature. For me personally, blessings are strengthened by clear intention, mental focus, and as little emotional connection to the recipient as possible -- with blessing as with divination, emotional connections tend to bollix things up. Blessings are weakened by the opposite of these things.

2) As a parent, as long as you have legal responsibility for your child you have spiritual responsibility as well, and that means you can pray for her without asking permission. It's best also to pray for wisdom for yourself, so your prayers will be guided for the benefit of all concerned.