You've met a great guy and want to spend more time together, but his divorce, his ex and his young daughter cast a shadow over your new relationship. Take your time getting to know your new man before taking on his daughter. If it's the right thing, he'll want to introduce you into his daughter's life as someone who is important to him. Your behavior should reassure her that you're not trying to take her mom's place. Enjoy your time as a couple, include his daughter when it's appropriate and be self-assured enough to realize her needs have to take precedence over your own.
One Step at a Time
No matter how much you and your new man are attracted to each other, you need to take the relationship slowly if he's a divorced dad. You two may be sure of your feelings for each other, but that dynamic can be significantly affected by his young daughter's reaction to her father dating. Initially, spend time together on occasions when the child is not with her father, so she doesn't feel you're encroaching on her time with Daddy. Don't push to meet his daughter until you're both sure of your own relationship, and by no means force him to choose between you and his little girl; his daughter's presence in his life is guaranteed, yours is not.
Just a Friend
The "go slow" approach applies not only to your relationship with the father but also to your involvement with his little girl. Don't push to meet her right away. Spend time getting to know the man first. In particular, pay attention to your conversations, how he talks about his daughter and his interactions with the girl's mother to get a sense of the existing family dynamic, and then proceed accordingly. If the divorce is bitter or recent, for example, introducing a girlfriend into the picture is probably not yet a good idea, so don't push for that to happen.
"You're Not My Mom!"
If he does decide to introduce you to his daughter, be friendly and relaxed, not pushy. She's right, you aren't her mom, and you're likely to upset her -- not to mention, his ex -- if you try to adopt that role. Don't take it personally if she doesn't warm up to you right away or compares you in unflattering terms to her mom. At this age, she might feel she is betraying her mom by being nice to you, even if she enjoys being with you. And, most importantly, under no circumstances should you criticize his ex in front of his daughter.
Make New Traditions
Even after you have met his daughter and she realizes you are going to be an important part of his life, continue to avoid behaviors and activities that put you in the position of "replacement mom." Don't allow yourself to fall into head-to-head competition with his ex. If Mom always bakes her favorite cookies for the first day of school, do something else to mark that day, such as getting her a funny card or taking her for ice cream the evening before. Find activities the three of you can enjoy together that don't "copy" what the girl does with Mom.