Time to talk to her psychiatrist and explain to he/she what you are seeing.
With a kid that age, it is hard to tell where bipolar leaves off and the hormonal / emotional imbalance of puberty picks up. It is hard to say if she has some rather typical difficulties with you because of her age, or if she just has pent up energy that time of day. Her meds could wear off that time of the day. It could be habitual at home behavior because she feels safe and can let it "all hang out."
I know, I am broken record about therapy. I'd go myself, if I were you. A counselor (don't see an LCSW, see someone with a Master's in Counseling) has been trained about adolescent behavior and can help you sort out what is teenage stuff from what is bipolar stuff. THey can also help YOU cope with your own feelings about this. If it seems reasonable after a time, find someone who specializes in teens to see your daughter. Give her a safe place to vent that doesn't always have to involve you. That would probably relieve some of your stress.
By the way, you don't have to have a bipolar teenager to feel overwhelmed by them. They are high energy people in the afternoons and into the late evenings. Their moods shift with the wind. They try on life roles and dreams the way some people try on clothes...even several "outfits" a day. Psychologically, they are experiencing an identity crisis. They are trying to figure out who they are, what they are about, what they can do mentally and physically, what they want for now and later. They do this with a general lack of sufficient sleep and weird eating patterns and in the face of the mixed messages of society. This is not a fun time for them either.
Hang in there.
The Lady Dragonfly
Yes, it was me...I know because I was there when I did it. Lupus sufferer, bipolar II sufferer. Currently on Indocin for chronic pericarditis related to lupus, and cherishing every deep breath without pain. Currently in graduate school for mental health counseling, class of Fall 2007. Vegan and loving it!