I don’t think it is necessary if you are happy with your essay and at the word limit. Mt. Holyoke does not accept by major – students are free to change from their intended major after they are admitted to the college.
If you want to play around with the essay a bit and see if you can slot in a sentence about why Mt Holyoke is a strong academic fit for your interests that is up to you.
The most important thing is for you to be happy with the essay and to have the essay reflect your reasons for wanting to attend Mt Holyoke.
Good luck.