Jealous of stepdaughter?

So I need some help because this is causing arguments with my bf and I, we've been together 2 and a half year's . But his daughter who is 9 has been irritating me on and off for a while .. today I thought I would plan a whole day together as a family so I thought it would be fun. Well it turns out she stuck to him like glue the WHOLE time and I never really got to enjoy the time together...and he seems to be in lala land and not even notice it... lately she's been missing her mom and I understand but I just can't express my feelings in a non bitchy way. I was never brought up with sharing emotions so it's tough . I just need help with any suggestions on how to deal with being a step mom. please help. I'm also 11w4d.