Being manipulative requires a cognitive level that no 8 month old baby has. She is, however, telling you she doesn't like the situation. My son was the same way at 6 months--with the sleeping part anyway. In that respect, I would say you have created a monster (I did too) and while it can be a difficult transition to getting them to sleep on their own when they've become used to our holding them, it's *so* completely worth the effort. I read "The Baby Whisperer" books (tempered with my own common sense and what works for me and my family) on getting them to sleep on their own--never had the stomach for the cry it out methods. We also started a bedtime routine: going for a slow walk around the block about a 1/2 hour before bedtime or cuddling together on the couch (something to start the calming process), then upstairs into pj's/diaper change, read 3-4 books always ending with Goodnight Moon or Big Red Barn, hugs & into bed, kiss goodnight and out the door. (then came the Baby Whisperer methods)
Honestly, it was rough the first 4-5 nights. We discovered it was a much smoother process if my husband did it. My presence made my son cry longer, I was his security blanket. Oh! Security blanket...we started using a little 'taggies' type blanket I made for him too. I made it little, 10x10 inches. I made sure to give it to him at times when we were cuddling, comforting, etc. so he would start associating the blanket (or whatever lovey) with comfort and not just me. Anyway, my husband took over bedtime for two weeks until our son was firmly into the routine and wasn't crying anymore (he stopped crying about a week into it) and then I joined them. Now virtually every night I leave his room with a big smile on my face because bedtime has become so lovely and not a struggle of "is he asleep enough to put him down and silently sprint for the door?" We did go through cycles of ease/difficulty with bedtime...it was more difficult if I let myself get lulled into thinking that because he was having an easy bedtime that I could hold him a couple mins longer. Then I'd do that for a while and he got used to it again so I'd be back to square one. Once you have a routine that works, don't stray from it by even a minute...at least not until your daughter's old enough to be told and understand "this is just for tonight." Don't worry, you won't be giving up cuddle time, you'll get it other times. My son is two now and he'll crawl into my lap, "Cuddle Mama." Melts my heart!
The biggest hurdle I had to get over was thinking that I was scarring him for life or that he was scared being alone in his room. You're teaching your daughter the skills she will need as she gets older to be confident in her own abilities to comfort herself. It's hard now but the benefits will *far* outweigh the difficulties!
As for the stranger anxiety...yes, it's a phase but I also believe that it can be aggravated because we are stay-at-home-moms. Our children don't have the opportunity to learn that we'll always come back or that they're okay without us as often as other children. Also, speaking for myself, my time is more flexible than if were to work outside the home, so we started out with no real routine at all. Starting a routine (the Baby Whisperer's EASY routine) was a huge help. You might try leaving her with a friend while you grocery shop or something shortish. (or start by leaving her with your husband--my husband and I negotiated for my getting Saturday mornings 'off'. I got to get out of the house alone for a couple hours every Saturday morning. It also gave my son & husband a chance to get to know each other, which helped with everything else!) Keep reassuring her and be confident in your tone of voice. Tell her what's going to happen, "I'm going to go put some clothes in the dryer and I'll be right back." Then do exactly that. I always held up one finger and said "I'll be right back" whenever I left his sight and then he started doing it back to me and saying "be back." Now I can catch his eye and hold up a finger and knows what's going on. At her age, your daughter takes a lot of her emotional cues from you. A little acting can help. Get excited when you're friend comes over, etc. When you come back into the room, don't go over and comfort immediately. Do one quick thing before you go to her. When you do go to her, don't pick her up and act like you're comforting, almost ignore that she was crying. I'd just do a quick, matter-of-fact, "you're okay" and quick one armed hug and jump in and start playing with the toys. That way you're close but you're not (for lack of a better word) indulging the behavior.
Remember, this too shall pass! It will require some work on your part to help her along...but it'll be *much* easier to do now than when she's older. You can do it!