Why won't my 8 month old sleep at night?

Try establishing a bedtime routine with her and keep it the same every night. For example, with my 9 month old we do bath, bottle, rock, and bed. She cries herself to sleep for about 5 minutes and then she's good all night. Try to not go in the room unless she cries for 15 minutes. Then if you do go in--keep the lights off, do not make eye contact, check her diaper, rock her back to sleep. Next time give her 20 minutes to cry then 25 and so on--this helps her realize that she can go longer. She should be able to sleep through the night at this age without waking to feed--she just needs to build up to that. White noise may help too that plays all night like a vaccuum or rain sounds--they sell machines or you can download some online. Just stay consistent and be strong--a little crying won't hurt her and you are actually helping her become move independent and preserving your own sanity. Try the same thing with naps--same time everyday, a routine (after lunch, snack, whatever)