If you can avoid taking her, do! Her lectures are poorly organized and she mostly just reads from the textbook. She also has a relatively strong accent and doesn't project very much, so it's hard to hear/understand her. Her midterms were okay, but she misspells a lot and the TA's had to clarify and actual changes parts of problems so they made sense.

My first quarter experience at UCLA was totally haunted by Prof. Ni. She has a think accent but to her credit she tried really hard.

After midterm1, I decided to quit her lectures and study from the textbook instead, just like everybody else.

I'm still trying to figure out how she got the job.

The review right below is very comprehensive. Sums up everything I had in mind.

tl;dr Avoid taking her, there are many many much better physics professors than Ni Ni

Let's run over the grading scheme really quick:
Homework: Mastering Physics, 17%
Quiz (given in discussion section): 3%. So basically attendance.
Midterm: 40%
Final: 40%

Overall experience: horrific.
I feel really bad for Professor Ni as she really cares about her students and tries really hard to teach, but there is a big difference between having the skills and trying hard.
She is an Assistant Professor, to my surprise, as barely anyone show up to her lectures.
The book does a much better than she does.
She does not give out minuses, so 30% A (A and A+), 30% B (B and B+), 30% C (C and C+). Nice grading scheme as it looks like, but her tests are really hard with the average on the midterms are, in order, 31% and 41%. She drop the lower curved score, but that is still a really low average.
I will have no problem with hard tests only if she teaches well, which is not the case here.
Her lectures are sometimes disorganized and incomprehensible. Her notes are illegible. She tries really hard to become better, but it just does not work.
She also put up videos and expect us to watch those before class, and I am pretty sure rarely anyone did that. The conceptual questions in class are interesting, but are not necessary.
In addition, Mastering Physics takes little time, and there is a problem with that because we are not given enough practice for her hard tests.
Overall, avoid taking her if you can. I just feel like her brilliance is only suitable for lab works rather than teaching.

Her demonstration is not that bad but the exams are extremely hard (class average ~40). HOWEVER she gives 30% A and 30% B which is very generous. Everything about her will be forgiven because of that fact. I like her.

Don't take her, enough said.

This was one of the worst, if not the worst, experience with a professor ever. It was impossible to understand her during lectures. And I mean impossible. Her accent is pretty heavy, so it wasn't her fault, but lectures were useless. She used another professor's powerpoints and reads off them. Her lectures got so bad that before the second midterm only around 30 students showed up out of a class of 200. What was even worse is that it was a 2 hour lecture twice a week.

The midterms were hard, to say the least. She allows an index card for the first one and two for the second one but they didn't help much. The averages were about 60% for both maybe slightly lower for the second one. The final was also ridiculously hard. She allowed three index cards for this one. About an hour in some people just gave up and turned in their exams early.

I know she tried her best and I think it was her first time teaching but avoid taking her like the plague. You won't be doing yourself any favors by choosing her over professors like Corbin or anyone else.