My baby hasnt been neutered/spayed yet where in the process of getting that done soon..but I have noticed today when I was giving her, her daily belly rub that she was leaking some yellow discharge

out of one of her breast is that normal/unnormal she hasnt been around males dogs to my knowledge(my mom takes her when I work) but I'm pretty sure that my mom is careful not to have her around male dog because neither one of us want her pergnant. I have called the vet but they are out of the office for some strange reason today (of course when I need help) but before I go hunting down every vet in the area, maybe I can get a lil help/reassurance from you guys before I go vet hunting lol......Thanks in advance