I believe her for several reasons

1. Trump is a cornered rat, desparate and thus lashing out would not be unusual in those circumstnces

2. Trump is a bully- maybe not all that physically courageous as you note, but his behavior in military school is revealing as well as shoving a foreign diplomat which is a physical altercation

3. As others pointed out, why put yourself out there under oath as she did given the nature of the MAGA crowd

4. finally, while under oath it is not a court of law and much of what she said was hearsay, but with this information, the committee now has more leads to pursue and witnesses to the actual events to subpoena