That sounds like a blatant lie and Shepard circles the tree, quietly observing the situation at hand. After a moment's deliberation she makes her decision.

"All right. When you fall down, I'll catch you. Unless you have the strength to sort of swing in my direction. Either way, I got you."

She knows for a fact that she can carry Lup. The hardest part here is getting through Lup's pride so that she can help her out.