No she's not wierd, you've probably not thought to work with her enough in the backyard. Odds are she sees that as a play/potty place, not a listen to momma place
Work with her in the backyard on lead for awhile to teach her that she has to listen there too.
You can teach her to sit from a down in one of two ways. For both ways, have her on leash, put her in a down and stand in front of her. You can either hold the loop of the lead in your right hand and slide your left hand up the leash -pretty much pulling her up into a sit - telling her to sit. OR you could get a really yummy treat and lure her into a sit. It probably won't take but a few minutes a day for maybe a day or two before she "gets it".
Good luck
You can teach her to sit from a down in one of two ways. For both ways, have her on leash, put her in a down and stand in front of her. You can either hold the loop of the lead in your right hand and slide your left hand up the leash -pretty much pulling her up into a sit - telling her to sit. OR you could get a really yummy treat and lure her into a sit. It probably won't take but a few minutes a day for maybe a day or two before she "gets it".
Good luck