When introducing your child to a probable new long-term partner, it's important to take things very gradually, for the sake of your child. Your child may be very anxious about the situation, so try to introduce your new friend slowly. Ask your child to tell you how she feels and what she thinks about your new relationship. Include your child in outings, if it's appropriate. Let the new relationship develop over time, to allow your child the time she needs to adjust.
Try to avoid a situation where your child has to adjust to several long-term partners during childhood. It's important to avoid having your child become attached to a person unless you believe that your relationship will become permanent. When children really care about people who end up leaving them, it becomes harder for them to let other people matter to them, for fear of another loss.
Your new friend shouldn't expect your child to warm up right away. Trying to be an 'instant parent,' particularly by disciplining a child, quickly builds resentment.
Struggles can usually be avoided by moving slowing, and not setting expectations too early and unrealistically. Be sensitive to your child's uncertainty and confused feelings.
Adjusting to new relationships takes time, but if your child shows increasing distress or hostility, consult your child's doctor or, if you are in Canada, and you wish to speak to a counsellor about this, contact Parent Help Line, 1-888-603-9100.