If I understand you correctly, I think you can fix this easier than you think. She was probably more concerned with being new, than with you. Just tell her you had stuff on your mind, apologize, make a big deal over her tomorrow, and carry on. I don't think you need to say "what" you had on your mind. Just tell her you hope she will forgive you and that you want to assure her that this is a great place to work. I know that my anxiety and bipolar make me get worked up way more than normal people do. So I would let yourself relax tonight, be good to yourself, and just know that this too shall pass. I have a DBT journal and that is one of the pages: THIS TOO SHALL PASS. I'm sure you are a great person. I'm sure she will be thrilled that you are reaching out to her tomorrow. Have a good evening.
:-) hugs!!!!