Perhaps. But developing the habit of thinking before saying "I can't" wasn't such a bad thing. Ultimately she was trying to cultivate in us the mindset of possibility and giving things a go, and it worked.
Years ago my ballet teacher took ownership of can't. Every time one of us said "I can't" we had to put 20 cents in the fundraising moneybox for the Guide Dog Association. She raised a fair bit of money that way. We must have been real wimps.
I actually had a person claim that he did own a word, several years and about three publishers ago. Said that if we didn't remove it immediately from the book in question, he'd sue. Claimed he'd copyrighted it.
Since then, I've been very careful not to use the word, so I don't have to pay royalties.