What Can I Do? I Don't Want To Lose Her.?

My best friend who I practically grew up with is really starting to get on my last nerve, and I really hate to say that about her because she's my best friend in the whole world (we're more like sisters). She's always been kind of a pessimist, and she'd always come to me to help her with her problems. And of course I was always more than happy to help. That's what friends are for. But lately it's been getting really bad. Like ever since she got married, got a job and all that crap, it's really taken a toll on her, and I'm the one who got all the 'venom' shot at me. Like this fun loving girl who I once knew has turned into somewhat of a snake. (We talk every night on instant messenger, so this is how she'll operate when she goes into her little 'snake' transformation. I'll say hi, she'll say hi back. That's like me going up to the snake and looking at it, and it's looking back at me. We'll start talking, saying a couple of random things, that's like the snake really checking me out, getting closer to me. Then there's long breaks of silence. That's when the snake gets ready to bite. Then after about a half an hour or so, there's this huge pessimistic rant in my face that I totally didn't deserve that came out of absolutely nowhere. The snake has struck, sunk her venomous fangs into me for no reason.) It's horrible. It's usually something to do with work (which I can totally understand, because work is stressful and sometimes you just need to let it all out) OR it has to do with hockey. That part I don't understand. She will go on these HUGE rants about her Flyers (expecting me to give a crap) for HOURS. It drives me crazy. Like to the point where I want to pull my hair out of my head. I just kind of sit there and let her rant because I really don't know what to say. I don't watch hockey, so I really don't know what to say back to her when she goes on these huge rants. Like one of her favorite players got traded, and she went on a rant to the point where she was in tears, and I just sat there and listened to her rant the whole time. I also know she's stressed because she just bought a new condo with her husband so she's in the process of moving out of her parent's house and into this new condo. I can certainly understand how stressful that can be. I mean, she's a newlywed, she has a job, she's moving out, that's all insanely stressful. But what bothers me, is I'm so afraid I'm going to lose her because I feel like all she ever does when we talk is complain. It's almost like complaining makes her happy. I try to offer suggestions on how she can be more optimistic and take it easy and stuff but she just throws them right out the window. Please help! I don't want to lose my best friend. (sorry this was so long, it was really emotional.)