I asked my thesis advisor to write me a letter of recommendation, giving her a copy of the letter of recommendation written by another professor for me the last time I applied to colleges. Turns out, she has submitted the same copy I sent her, with a few minor changes. While, this is not problematic per se, I am applying to a few colleges that I had also applied to last time. Will the admissions office view this negatively, considering pretty much the same letter has been sent by two different individuals in consecutive years?
No, that's not a big issue for you. I'd be very surprised if anyone sees that the letters are similar (who would compare letters of recommendations between two different years?). And if they do notice and are interested in you, they can always contact your thesis advisor (it does reflect a bit strange on her tbh).