Don't step in, in fact leave the building. Go get your nails done, or go for a bike ride, go visit friends. She has to learn about him and that he can care for her and she'll be ok. You have to leave her with him to get to know him. You have to break the mom/daughter attachment at the hip problem. And that really will be a problem when she gets older. 18 months is really when separation anxiety makes it's appearance, so it will be even more difficult given her age. But, with constant reassuring from you and dad, she'll learn to love him as much as you and be a very well balanced child :-)

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