The forum isn't anywhere near as active as it used to be, but there are two of us here almost every day.
I'm the newbie, so you might want to wait for my mentor. In the meantime, my own suggestion would be to open it just a bit and reward Marcie for pushing it open the rest of the way. Have fun and be silly, she's a dog and she'll love it.
Then gradually open it less and less of a bit until it is closed.
My understanding is that dogs can't learn from their siblings' example when it comes to training.
Bummer! That's the only downside of my new doggie daughter, lol.
Marcie sounds like a gem. Laurel's trainer assures me that you absolutely CAN and SHOULD teach old dogs new tricks, so that old chestnut is absolutely nothing like "just like riding a bicycle" which really IS "just like riding a bicycle" in case you don't ride bicycles.