1)
Why did she say "Haloch Elech"?
1.
Malbim: I will go with you, both to Kedesh (to recruit soldiers) and to the war (refer to 4:8:1:1*).
2)
What is the meaning of "v'Yad Ishah Yimkor..."?
1.
Radak #1: Ya'el will kill Sisera. 1
2.
Radak #2: If I go with you, the victory will not be attributed to you, rather, to me.
3.
Malbim: Had you gone alone, gathering the men all would have been attributed to you (they heeded you), and also killing Sisera. Now, gathering will be due to me, and Ya'el will kill Sisera.