Havanese is constantly whining/wanting to see a dog that she does not know

This started this morning. When we went on our morning walks, she started running down to the end of the block and we came to this apartment with a gate and a dog sitting outside. Ginger (my dog) started to whine and growl, getting down into her play bow, and she stood on her hind legs to try and see the dog better.

Usually, this dog would bark and growl at her, and Ginger would growl back and try to lunge. This time, the dog didn't bark at her, and just watched her as she whined and went crazy. I led her away, but she kept trying to stand up on her hind legs and see the dog. She kept trying to go back to the apartment, so I picked her up and carried her home.

The same thing just happened tonight; she was whining like crazy so we took her out and she sniffed a few bushes, before running down to that same apartment and this time we let her go to the gate and sniff it because no one was out there. She tried to climb through the gate, so we grabbed her and carried her farther from the apartment. We set her down, and she went back normal again (sniffing and peeing on bushes). At the very end of the walk, she started to try and run back to the apartment and if we tried to stop her and lead her away, she would just stand in place and not move. We had to pick her up and bring her home.

This is such a crazy behavior for her. She's normally more on the aggressive side towards dogs she doesn't know/dogs that bark and growl at her, and usually is a dog that roughhouses often. I'm just searching for answers here, honestly. I really want to know why she is doing this, and if anyone has had this (or similar) behavior in their dog/other dogs.