K.B.
My son had an imaginary friend who he called "Henny Menny" (I found out later it was Handy Manny from the TV show).
Anyway, to nip her stalling in the bud, try to remember to always include Jessica. When it's time to leave, tell her AND Jessica to put their coats on, etc. If you make sure Jessica is always included, she won't need to go get her. Eventually, she'll grow out of it. Handy Manny didn't stick around too long. Every now and then, he visits but that's about it.