1)
Why did she say "I prayed for this youth"?
1.
Rashi from Brachos 31b: Eli had suggested that he will kill him, and pray for her to have a better child.
2.
Malbim: She gave additional reasons why Eli should accept to raise Shmuel. (c) He was born just like I asked - a male, Zera Anashim (not outstanding), proper to stand in the King's palace. (d) Hashem gave him to me (conception) immediately after I prayed. (e) He gave what I requested directly from Him, amidst Chesed. (f) I prayed on condition that he will be give to Hashem, like I vowed. (g) Do not say that I will give him to Hashem later, His entire life, he is to Hashem (verse 28)!
