I met my boyfriend when his daughter was only a year old and she is now 4. Her mother had left when she was 3 months so when we started dating she assumed I was her mother and I've been raising her as my own and we've been a happy family except she gets jealous of her father and me any time we talk or show eachother affection. I don't really think she remember her real mom or the time that it was just her and her dad but i don't know why else she would get this way and she switches sometimes it's towards me and others its him. It's causing a lot of tension between the 3 of us what should we do ?

Does she have you all to herself during the day?
If so she maybe so used to your constant attention all day and then feel left out when her dad comes home!
Perhaps you could try including her in your cuddles and maybe all of you do an activity of her choice.
It will soon get better, it is just she feels left out, some children do behave like this at times, I don't think she would remember her mum as she is only very small still. I have a 5 yr old girl whose dad walked out when she was 9 months old, she doesn't remember him at all, she calls my new husband dad because thats all she has ever known.
I hope this helps you.

I know that there is a stage of development between the ages of 2 and 5 where a child is jealous of the same gender parent. She wants to be "in love" with her dad the way you are and have the affection you do. It's a "piece" of him that she doesn't have, only you do. It takes some time for them to accept that they can't play every role to both of you. I have a son who has gone through it and I explained how nothing can take his place but that his dad and I need some of our own time, just like my son and I need some of our own time. Good luck! It will pass.