Well, I do think it's important. She wanted someone to give her an opening to secure the orb, or to secure the orb the time she fights him.
Laxus wanted to destroy it. So he didn't care about collateral damage and break the orb in action, even accidentally.
Thinking about Natsu or Grey is a respect to their powers. The one who faces him must have enough ressources to deal with him for a while.
Thinking that Grey is weak is a joke. Erza doesn't underrate them (Natsu-Grey).
As Erza had no help, she tryed to stop Laxus by her own to protect the orb. The fact is that without Kyria, Erza could accomplish her missions :
- Neutralise Laxus even if she felt with him.
- Protect the Orb without securing it.