Preceptor talking bad about me behind my back

I’m a new grad who has been working postpartum at my hospital for about 10 months. At our hospital, it’s standard that once you complete close to a year of postpartum nursing, you move on to L&D nursing. We have 18 total labour training shifts with a preceptor - my preceptor has been giving me good fairly good feedback, that I know all the steps I just need to get faster and that comes with time. But now, this preceptor is on vacation and I have a new one for my last few shifts. This nurse is known for being very blunt and as some of my coworkers have said “mean”. Anyways, on my 4th last shift she was acting very cold towards me, any minor mistake I would make or anything I needed to be reminded about she would get angry at me. She then had a long conversation with me after our patient delivered that I needed to be faster at basically everything and work on prioritizing/time management, but that it’s nothing that she’s worried about. I appreciated the feedback, but after the shift, my work friend told me she overheard her speaking to another nurse in a very angry tone about how poorly I’m doing and I have 3 shifts left and I can’t be moving this slow and my priorities are completely wrong. The delivery went quite smoothly however, everything was set up and ready way ahead of time and I did everything on my own, just maybe not as fast as a nurse with 10+ years experience. I had a feeling with being fairly new and my preceptors being close to the other staff that they would be talking about me and my performance when I’m not there, but I didn’t think it would be this negative, especially when she told me to my face that it wasn’t a major concern. I’m feeling extremely discouraged and unable to stop cycling through the scenario thinking about her feedback and her talking about me behind my back and wondering what could I have done differently with my patient. My biggest fear is her telling a manager that I’m not ready or cut out for L&D, or telling them I need more shifts, since then the whole staff will be talking about it (I know more shifts aren’t a bad thing but it just worries me). I’m ultimately terrified to be on my own though, and scared that despite how hard I try, I won’t see improvements in my speed and will keep making stupid mistakes. Anything anyone can suggest in this situation lol? Should I ask for more training? Is my preceptor in the right? Or should I just keep pushing through?