Here's an email and observation that I received from someone who has their dog's ashes. They
experienced how ashes can connect to the energy of spirit.
I got my dog's ashes back today. I also selected a necklace with a heart and some of her cremains were placed inside the locket. I put it on and placed my left palm over the locket and pressed it close to my heart. For two seconds and only two seconds, I felt a soft electrical type of charge. I was shocked and immediately felt peace.
I could not believe what I felt so I tried it again and again but there was no other feeling. It was a one time occurrence and I am still in a state of peace and happiness. I believe it was her spirit that was now resting with me on my heart.
What a wonderful tribute to her to keep some of her ashes in a locket- and a great sign from her that she's still with you! When we pass the energy within our physical bodies couple with our memories and personalities and we make a choice to stay Earth-bound as a ghost or cross over into the light/heaven/Valhalla, etc. as a spirit. Energy is the key here and love is positive emotional energy that binds us together with those we love (whether pet or person).
Sometimes ashes can hold some residual energies. The energy can be physically sensed some times, and it appears that your girl made it happen for you. Your emotional energy (love) helped "re-energize" the residual energy in your dog's ashes, so you felt a spark.
Take comfort in knowing she's still with you in spirit.
For more information about pet spirits, check out "Pets and the Afterlife" by Rob Gutro, available in paperback and E-book on Amazon.com.