1)
Why does it mention Shelamim?
1.
Rashi: I prepared a big meal, for today I offered the Shelamim that I vowed.
2.
Malbim: She tells him that she invites him to a Seudas Mitzvah, to eat meat of Shelamim. For her, it is Simchah of Mitzvah - she fulfilled her vow. The Yetzer ha'Ra begins with a Mitzvah!