Re Lil I think telling her that you don't want to listen to negative stuff is totally reasonable... tell her that if she persists, then every time she starts complaining, you're going to go off somewhere and be cheerful by yourself until she can see the world in a better light. I have done that a few times, I need to do it more.
(part "A")I took this to mean that you do not want to act moody, and (part "B")you also do not want to act in ways that she will interpret as moody. Part "A" is the negavity and opinionated talk of BB grates on me and wears my good mood down till I start getting moody or start to act withdrawn.
When I say I don't want to act withdrawn / moody, I am saying I resist acting that way but find it difficult to do given some of the circumstances on some days. My choice, if I had it, would be interacting with some one, preferably BB, that was more congenial / friendly / compatible.
Part "B" I am not trying to control how she interprets my withdrawn / moody state. I know she will think what she thinks and I quit trying to change what she sees/hears/reasons and interprets from that.
Some examples, I know I am not going to convince BB it is not too warm to go some where, or one of her friends is not too busy for her to call and visit on the phone for 15 minuets.
Well, if you don't want to act moody, then don't. Period. If I find myself becoming too withdrawn / moody I usually find things to do away from BB. This helps for now and I am seeing I don't get bogged down as much in BB's tar pit. I might even try some PBTS tonight.