"Campbell is my best friend!"

Maggie said this several times after having our best friends over for a playdate.  I was so excited!  Then I started thinking that she very well could be saying that because I have encouraged her to think of Campbell as her best friend (and when I say "encouraged", I mean I point blank said "Campbell is your best friend.")  Should I feel guilty about that?  As of right now, I am enjoying every minute of it, and I am simply loving the fact that my plan is working out so beautifully.  Do you think this same brainwashing method will work with boyfriends when she is a teenager?