Yes marijuana is difficult to have in combination with bipolar meds. A lot of people may disagree but I think that both are comparable in the therapeutic effects they offer. However it has to be one or the other. Pot is complicated because I smoked it when I was young if I was too happy it would bring me down and if I was too depressed it would bring me up. I actually didn't know I was bipolar until about a month ago but it only affirmed what I already knew about my childhood.
Anyway, the meds she is taking are going to be more beneficial that the marijuana, but I understand that she is in pain. The thing is I would look for other avenues of pain reduction that do not include cannibas or narcotics as all of these will mess with the therapeutic level of her meds.
Good Luck and welcome to the Forum.
medication effects everyone differently, so i couldn't say for certain. my best friend is bipolar and smoked pot for most of her teen years - it did not interact with her medication. she might have been on different meds tho. she DID start having some very serious and VERY SCARY problems when she mixed her meds with alcohol, i had to physically restrain her on more than one occassion to keep her from hurting herself or others. sometimes she didn't even know who i was. people think they can just have a beer or something and they really can't. mixing with other narcotics like painkillers and amphetamines can cause some of that anger too.
anyway i hope things get better. i doubt it's the pot but it's worth talking to a doc about, and make sure she gets therapy talking with someone can help so much.