How do i stop my 7 yr old daughter from manipulating me to get whatever she wants?

My 7yr old daughter is becoming a master manipulator to get whatever she wants.I'm a single mother working fulltime.So sometimes i feel guilty for not spending as much time with her then i did before.Lately it seems like she's manipulating me & trying to make me feel bad for her. She started having problems with her stomach about 2 months ago & started manipulating me so she could stay up late and to get more attention from me.I spend almost all my free time with her playing and watching T.V. but it seems like nothing i do is good enough.We live with my BF who i've been with since she was 3 & it's easier for him to see when she doing this and bring it to my attention.She is also having problems with her real dad.She sees him 1x week.He lives with his mom whom takes care of her when she is over there.Her dad spends about 1 hour with her and then takes off he's an alcoholic so drinking comes first.This breaks my heart and she knows how to use it to her advantage.How do i stop this?