Lengwei is that protective best friend *in a good way* you'd want to have in your life

Yes

She is but right now she's getting between us and our boys I want rourou to have his two dads.
So, anyone trying to separate them to me is my enemies

I think there's a reason behind it. If you look at it, i doesn't feel like he likes him, it's somewhat "being afraid of something she badly experienced that might happen to her friend" she somehow gives off this vibe