Dear Friend,
All have done here in, your concern for your daughter is really appreciable, yet, try to put your daughter on her own, Every bird fly its own.. let her come out with good questions of why she could not go through, despite of having a good academic achievement? Ask her go to her teachers/mentors, certainly some one find the thread where it is woven weak they will guide her, also, never trust who praise her as, the praise is the weapon deliberately put her down. Attending interview and preparing for the same is a matter of persistence approach, attitude, presence of mind, good communication and confidence. She should also know the company with whom she is going to work well in advance at least about the product/service/market presence/brand value etc., this will help her in going through the interview.
Further, never ask why she could not get through the interview, make her, your kit is not this, you get the more and your goal is beyond this one, ask her to sit, get a note book make her to write the incident(interview) in detail whatever she remember this skill certainly help her where she should have given a better response, also this will enhance her language of presence. A self analysis is a must for her life.
You know there is always a perception that we are being interviewed by the most skillful, intelligent, the best in all counts..the reality is the contra of our presumption, sometimes, we are being interviewed by, who never now the subject those are the occasion frustrating, belittle and unpraiseworthy, but, they are at the helm, they teach us patience, how to deal the circumstances etc., these are the things your daughter will learn by her own, you should have a beautiful talk, be friendly with her..
As regard your concern for best coaching for soft skills, now a days a lot of people available who counsel your daughter, guide her for a better prospects for that get in touch with the local teachers they will guide you, some people are being trained by online try to find out a good one, never go for the best, because, you are not the one can judge it..soft skill is a subject is becoming familiar in the recent past. Also, go for short term courses for skill development...
best of luck...we are human be humane...