After Elena gave Agripuna permission to touch Echidna, she immediately started to poke him. Then after feeling now wobbly and bubbly this cute little slime was, Agripuna got rid of the slight apprehension that she was feeling and tried to gently hug Echidna. Echidna was a spoiled child who really liked to cuddle with others, so she was extremely cooperative and even hugged Agripuna back.
This made Agripuna to feel blissful. This was exactly the type of being that she was trying so hard to create. To anyone else Echidna would look the same as any other slime but as someone who had researched slimes for a major part of her life, Agripuna was able to understand that Echidna was not any normal slime but was the pinnacle that a slime could reach.