My friend

She calls me everyday. She's super sweet and I love her to death but she calls me everyday right when I'm trying to do something. I'm 34 weeks pregnant and take naps during the day and the evening time is my time to get things together...but she calls me and I can't get much done with her on the phone. I try to steer the conversation to say I need to get off the phone and shell still end up talking to me for an hour or so. And it's never about anything important, just complaints, work, what she wants to do etc. I'm such a push over...how do I tell her?