Can I use "if there are ~" instead of "if there were ~"?
No, it would not sound the same to say "if there are" instead of "if there were" in this case. This is because she is talking about something which could have existed in a hypothetical situation contrary to what actually exists. Since there are no real "seven deadly grammar sins", they do not actually exist and so she uses "were" instead of "are" because "were" is subjunctive and expresses a condition contrary to the facts.
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