I never agreed with Lisa's attitude towards the group, but...
..her displeasure with her membership in TLC was made perfectly clear to me when I saw this movie.
Don't get me wrong, I've purchased all of their albums and loved their songs, but it wasn't until I saw the creation of so many of their hit singles represented by this film, that I understood why Lisa eventually grew disenchanted with being a member: there really wasn't much for her to do!
Think about it. After "Oooooh on the TLC Tip," which ultimately proved their best album in terms of group representation (affording Lisa visibility on at least half the tracks), TLC segued into a sexier and more adult sound, which was made evident by the videos for "Creep" and "Red Light Special." Aside from the rap on "Waterfalls," (the only CSC single featuring Left Eye vocals), Lisa had bars on "Kick Your Game," "Sumthin Wicked This Way Comes" and "Switch." What does that add up to? Lisa on 4/11 songs for CSC.
IMO this trend continued with FanMail; the initial version of the album didn't even feature Lisa's rap on "No Scrubs," and even in 1999 I felt as though the addition of her vocals to the radio/video versions seemed to be an afterthought, as though the producers and TLC had listened to the entire album and realized there really wasn't much Left Eye on it.
What else on FanMail did she get? Bars on "I'm Good at Being Bad," "If They Knew," "My Life" and "Shout", which totals 5/14 songs with Left Eye verses, if you count the single edit of "No Scrubs."
So there you have it, and like I said, I didn't get it myself until I saw the "recording footage" clips in the movie when the girls were making the albums. She probably felt like she was being under-utilized, so it's no wonder she wanted to break out and do her own thing. I don't think she handled it the best way by acting up when they had promotional duties, but I didn't ever really think her desire for solo stardom was valid until seeing how many of the group's hit singles don't feature her on them (at least in terms of lead vocals).