You are welcome Shifty.
It is not uncommon to lose confidence when it comes to asking a girl out.
However, the less you think about it, the less likely you will create all kinds of negative stories in your mind about how she will react to it.
With that in mind, try not to think too hard about it in the next 2 days before you are able to meet up with her again at school.
Focus on other activities and thoughts.
The less time you spend thinking about it, the less likely you will psych yourself out of asking her out.
Looking forward to finding out how it went.
All the best.