Wife's best friend is obsessed with us what should we do?

my wife and I married straight out of high school and have been married many years now. During college we occasionally let her good friend stay with us because she had no where else to go. She's a pretty girl but painfully shy and socially backward with little to no friends outside of my wife and me by default.
after a year I think she started becoming really interested in our sex life. My wife kept it at arms length at first but then her friend kept asking about it, even going so far as to ask to watch us have sex. My wife said no but after many times asking her she thought it might be fun. She asked me and hell yeah I thought it would be fun. We invited her in one night and she could watch but no join us. My wife and I put on a show as it was so hot to have someone watch. We glanced over a few times to see her friend hard at work masturbating.
Since then the girl won't leave us alone. She sends me emails at work and wants to know when can she see me again? She calls my wife at work and says I'm just thinking about you? Several times my wife swears she's heard her Outsdie our door when we've had sex recently...
What should we do? I say kick her out but my wife says we kinda did create the problem so we need to know how to fix it...
Wife's best friend is obsessed with us what should we do?
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