ok so, my MIL is a monster. she is basically all about herself until she needs something then she…

ok so, my MIL is a monster. she is basically all about herself until she needs something then she kisses our asses hardcore. I definitely am NOT telling her I'm pregnant with baby #2 but I might have to see her soon. at a bbq with alcohol. she is basically an alcoholic. we aren't bringing my 2yr to this bbq because I don't want her seeing him especially when she's drunk. she hasn't seen us in over a year so she will probably kiss out asses and follow me around the whole time. how can I hide my sickness and not drinking for a whole bbq, I know my hubby will stay for a while. plus I'm a little rounder in the middle than before! so baggy shirt? and empty beer bottle?