If she feels close to her, a fatherless daughter will naturally turn to her mother for comfort and support when feeling anguish over her dad's absence. Sadly, though, a mom in this situation may be ill-suited to provide the understanding that her daughter seeks. The reason for this is quite simple: a mom may be struggling with tremendous guilt for having had sex with a man who wound up being such an irresponsible father.
Therefore, when her daughter turns to her, she may react with hostility and defensiveness rather than compassion. This reaction can shock the daughter and cause her to shut down emotionally. It can cause her to bottle up her pain, leading to depression and self-destructive behaviors. That's why it's important for fatherless daughters to be discerning when sharing their grief. It's also why I highly recommend they talk with a therapist, an objective professional who's trained to listen and offer sound advice.
I've heard from countless fatherless daughters who desperately wanted their moms to validate their pain, only to hear comments such as “just get over it” and “I'm doing all I can for you and you're so ungrateful” and “other people have it a lot worse than you.” Needless to say, these kind of remarks are not empathetic and not at all helpful. Sometimes, though, a mom is just too overwhelmed with her own responsibilities and has nothing left to give.
In your heart of hearts, you must have a good idea whether or not to trust your mother with this pain. Perhaps, it's just too hard to accept that you can't. However, part of maturing is realizing that our moms are humans and have limitations just like everyone else.
I recommend you tell your mother that you want to see a therapist to discuss your dad's absence. The therapist, in turn, may bring your mother into one or more of the sessions to facilitate a conversation between the two of you. That could really bring about understanding and make your relationship stronger.