I already sent one 5 days ago and she said she was working on it. However the deadline is really close now (30/11). Should I send a second reminder now?
If this is for an application for a US graduate program, the due dates for the main application are stricter than for recommendations. The admission or review committee likely won't meet until next year. I had an advisor that had a habit of submitting these things a few days after they were supposed to be submitted and it was never a problem. Since they acknowledged your reminder email, I suggest you leave them alone. If you arrive at the due date with no submission, then you can send another polite reminder if you feel like its necessary.
Professors forget things too, but you've already reminded them, you don't want to remind them again unless you have an indicator it's been forgotten. But, it seems you don't want to remind, you just want to know when it is sent.
You could send them a message asking for confirmation when it has been sent. This is common in office settings when multiple people are involved. For example:
"Dear Professor So-N-So: I am very anxious about this application, I have forgotten to ask if you would be able to let me know when it is completed. Having that confirmation would be a great relief to me. Thank you for your time, Me".