submissive peeing?

my gsd mix, who i adopted a little over 3 months ago, has had a serious problem with my SO's sister's new 4 mo female gsd mix. she snarled and growled when around her, to the point we couldn't take them off leash together.

finally, this past weekend, we felt comfortable doing so, and they played and wrestled for hours. it was amazing. we were all so happy and relieved that they finally can get along.

anyway, this afternoon my SO took olive, my dog, over to their house for another play date. their dog, nita, has a tendency to pee a little when she gets too excited. which she did upon olive's arrival. then later on they went out back, and were wrestling on the porch, with nita on top. olive ended up peeing a little then. what could that mean??

it's very uncharacteristic of her to pee unless she's intentionally going potty. is this some type of submission, or what? i'm really curious.

thanks!