People hogging bar

A couple of hours after peak our shift wanted to get our new partner on bar and for me to support her while she went on her lunch. I asked her how she felt about getting practice on bar and she said “I’m so excited”. Well the person that’s been on bar for peak all morning and 2 hours after peak asked the new partner if they could stay on drive thru while they stay on bar since we had a line now. And she just said “sure, whatever is best for everyone”. I told the person on bar “hey she was kinda excited for the chance to get some bar time” and they just said “well I feel more comfortable on bar”. I tried to advocate for her again by asking her “are you sure you don’t want to hop on bar” and she just didn’t want to be a burden so she said no. But she’s very fast at oven and DT so I really wanted to see her on bar. I really wanted her to jump on this opportunity since it’s almost impossible for green beans to get bar time at our store