HELP! Need advice

Need some advice on how to deal with a particular issue I’m having. A little background about myself, I’ve got hired a part time position (3 days a week) for a new customer service job taking food orders for different fast food companies. So basically my first week at the job I had taken some calls while my trainer was listening in on the same line. Had a customer who seemed pretty on edge and in a “rush” as well. Her accent was thick so it was hard to understand what she wanted ordered plus she spoke really fast to make it worse. Although I tried my best I still stumbled a lot as I was nervous and it was my 3rd day at the job.

Anyways moving on from there today (7th day on the job) I was still in training and happened to take more calls. Only this time my trainer had run out to go the washroom and lone behold I encounter the same customer as before. She explained that she had 2 separate orders to place. I proceeded to take her 1st order and again had issues so I told her to repeat numbers multiple times as I was losing track for what she was saying. She started to moan and say “I don’t have all day” I replied by saying “sorry ma’am I’m still training” and she said “I know you have been since 3 weeks ago”. After this there was no issues in the rest of her order and before she left I told her “thank you for your patience, have a nice day” and she seemed happier at the end maybe because I picked it up towards the end of the order but idk. Remember this was only the first order and she had hung up like she was finished. But she would call back 5 min later and this time my trainer (not knowing what happened) would speak to her, she took her order in half the time I did which was kind of disheartening. But what crushed any confidence I had was that this customer lady told my trainer “wow you’re really fast thank you” at the end of the call while I was on the other line listening.

My only issue is that she practically meant I should be more competent at the job because it’s been “3 weeks” but in reality Im part time and have barely worked a full 7 days so far. On top of that training consists of 100’s of other things, sure if I was taking orders for 7 days straight I would be more proficient but I’ve only taken about 40 min worth of calls so far. I just don’t know if I’m the one In the wrong here or it’s vice versa, my coworkers told me to not worry about it as this customer has always been like that. I know I will encounter her as a customer again, how should I approach them ? I don’t want to be her punching bag during my time at this job lol