Who cares if you misspell words on your internship cover letter? Normally people just don't care. I can't stand the people that preach about how to create such a perfect document. The internship cover letter is not the end goal. Creating a piece of paper, just doesn't matter. Connections matter more.
Do not spend forever editing your internship cover letter. It just doesn't make sense for any student to do that. Time is valuable and better spent building relationships or creating something of value.
Also, college recruiters have to get over themselves. Seriously, it just doesn't matter how perfect you think you are, great innovators sometime make spelling mistakes. I would argue that they make more spelling mistakes than the average person because they are confident enough to not care about internship cover letter perfection. Instead, they care about doing things!
Don't waste your time or get rattled based on ruthless recruiters.