ONE person making a negative assessment of you says FAR more about them than you!
This is almost verbatim what my personal tutor said to me when I had a similar issue during nurse training. I was young, naive, very hurt and worried sick it would impact my results.
It later emerged the person assessing me had taken against me simply because I had commented from a place of innocence and still learning myself on something she did that I thought merely odd, but that was a mistake she could have got in a lot of trouble over. She was trying to discredit me ahead of time in case I mentioned it to someone else.
That they're giving such weight to ONE persons likely prejudicial account with zero evidence would make me think twice too
However, what I will say, if you're wanting to go into nursing, you're going to deal with MUCH worse than this so I'm afraid there's an element of you needing to develop a thicker skin and a determination to prove them wrong
I was slim, young and blonde and booby when I did my nurse training I was frequently falsely perceived as a bimbo at the start of placements, by working hard, being willing to do whatever necessary and developing a good therapeutic relationship with patients I proved all but that one wrong.
I'm now short fat and grey and the boobs have dropped 
I would be asking why they are taking this feedback from ONE person compared to the feedback from all the others?
Yes I would too - but worded carefully
Maybe "I appreciate you taking the time to discuss this with me. However, I am concerned that the positive feedback from everyone else I worked with during this training is not being given its due respect. I am of course concerned that X Thought of me as unsuited to the role, but without specific examples I would like to know exactly why they formed that opinion. Is it possible that they misinterpreted my manner for some reason outwith my control? I would like to perhaps have a meeting with all 3 of us to discuss this and find a way to move forward. Also if I am to undertake a further weeks training and assessment I think it only fair that this be with someone other than her so that the assessment isn't coloured by previous experiences"
I am a registered nurse and unfortunately you do encounter people like this from time to time in this profession
Totally agree!
Some nurses and other hcps just HATE newbies and hate doing training etc but it's part of the job.
Sensible management knows who they are and pay their opinions little heed.
Which is why I said this is something you kinda need to get used to.
Several on my course fell foul of the orthopaedic nurse mentor, I was DREADING that placement she had earned the unfortunate nickname "dragon bones" but actually when I was on that placement I did well and she gave me an excellent assessment and even said once I completed training to let her know "I'll find you a job here I'll bloody invent one!" I think not because I was a better trainee just her methods suited me (extremely precise instructions (I have what was then undx ocd I'm very detail oriented - this is not always a good thing in nursing, "old school" methods favoured, stickler for the rules - I was a military brat I'm always very punctual, very rule following) I responded very well to her mentoring as I knew exactly where I stood with her. Plus I'm the type to not make excuses if I fuck up, I say "sorry you're right won't happen again" and she was a straight talker, we also had a similar fairly dark sense of humour which I think the other trainees hadn't yet developed.
Another mentor the others all got along really well with I did ok on the assessment but I really didn't enjoy working with her as I found her too vague, too undisciplined and didn't give enough direction. The others liked that placement as it was an "easy" one.
@unim sadly that can be an issue as can prejudice against newbies in general, better educated applicants, applicants of particular religions (I've worked in Catholic care homes where there's a preconceived idea that Protestant carers are "cold"), single mothers... people can be bigoted arses!
But trust me patients are MUCH more blunt and harsh as are their loved ones.
You tend to find they don't do a whole lot of work themselves but spend a lot of time criticising
Yep! They tend to be worried an enthusiastic newbie will show them up, they also tend to be "passed over" for promotion - actually not promoted as they're lazy and often incompetent, but they think they're the bees knees and "in charge" cos they've been there so long! Doesn't occur to them they haven't advanced cos they're shit!
Your decision but I think you need to consider that nursing IS a tough job and you will get far worse thrown at you than this - verbally AND physically. You need to be able to bat it off and crack on or else it'll really stress you out