How can I get my puppy to stop trying to nurse?

I got a puppy 2 weeks ago, and now she is 14 weeks old. My 3 year old dog has nipples because she nursed a puppy we took in 2 years ago. My 3 year old dog is fixed but she still has the nipples. My new puppy won't leave her alone. She is always licking or bitting her nipples. I'm not sure if she is trying to nurse or just playing. But my 3 year old dog comes up to me with her belly soaked in slobber. It really irritates my 3 year old dog and I can't get my puppy to stop. I clap my hands really loud and tell her no every time she does is, but she doesn't listen. Do you think with consistency she will learn? Or should I try something different? Thanks.

It sounds like your older dog is a little timid? Most dogs would be able to put a stop to this on their own. A spray bottle may be helpful in this situation. Just squirt the pup with a little water when he's bugging your other dog this way.

Poor breader and not weened properly, no clapping hands will not work. crate training might help, I would look for professional help.

It appears you got the puppy at 12 weeks so this is not a matter of being taken from the mother dog at too early an age. The dog would have been completely weaned from nursing. The puppy is bullying the adult dog.Do not allow the puppy to bully the adult dog. Put up a gate. Each time the puppy goes for a nipple, NO, pick her up an put her on the other side of the gate with a chew toy, with no eye contact. Do not give the puppy any attention, just go about your business. When the puppy is calm and not barking or whining, let her back into the room. When she makes a move on the adult dog again, same thing, NO, and put her on the other side of the gate. You have to be consistent. If you are not, you are teaching the puppy that she is dominate and can bully the adult dog at will.