I use those glue traps every year, to catch the mice that sneak into our house with the first cold spell.(I can't bear to use a spring-type mouse trap- ) Then I drive out in the country, with the mouse stuck on the glue trap sitting at the bottom of an empty bucket.
Like "gemstone" suggested-- I use a little vegetable oil by the mouse's feet--- and viola!!--- the mouse runs off the trap and scurries across the open land in search of a bush to hide under and then to hopefully dig a hole there and have a new home.

I hope you got your sister's pet freed.

mandy