I think she didn't try to eat him, she tried to scare him. The reason she did that is I think she is the one who ate lab guys father and now she regrets it and doesn't want to do it to Mikane. She didn't want Mikane to get attached to her like the father did before, she talks a lot about sadness and I think that is one of the reasons.
Also, extremely sad for Yukko in all this, she gets treated as a second thought for him.