Quick reply, no this lying and false accusations is not a common trait of Bipolars, it is another disorder or just her nature to be a liar, I am sure.
Many things may have happened to her over the years, that may have caused her to either seek attention by false accusations, resentment, peer group influences, etc.
But no, this is not to be attributed to her DX.
The best thing or person should I say, is her pdoc, he or she can give you more info.
I am not an expert, to say for sure, but I haven't heard of such thing as false accusations of this nature, being related to Bipolar disorder. It is possible she has multiple disorders, it does occur, many of us do carry several DX's besides just one DX.
I wish I could of offered you more exact info., but the best I can do is offer and/or pass any info I have learned about Bipolar and experienced, this disorder runs in my family.
I wish you lots of luck with this, please take care.

DE