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I have tried ignoring the door, despite her persistency (she'll stand there for ages hammering and ringing) and there is no point in speaking to the parents as she is a typical spoilt only child of older, working patents who appear to think that she can do no wrong and allow her to speak to them like dirt. I have considered keeping the ball or puncturing it but as my grandchildren visit me there may possibly be an occasion at some point when their ball ends up in her garden, in which case I would like to retrieve it in tact. Looks like I'm stuck but thanks for your input. Maybe "kill the kid" is worth considering eh.