It is difficult to advise as to the 'best' choice because ultimately, this is your life and people you have to be with...

You can either 'suck it up', be polite and endure her words and presence or stay firm in your boundaries (nothing wrong with that) and avoid her as you have enough on your plate at the moment. It is not about being a 'big baby' but about setting boundaries and self-care. You deserve respect. You don't deserve abuse from *anyone* Most likely, she won't change her behaviour. You can only change your behaviour and/or how you respond to her.

Check-in with yourself to see which 'choice' sits best with you.

There is nothing wrong if you choose to 'suck it up' or is you stick to your decision. Which decision could you live with, without regret-guilt and/or beating yourself up either in the moment or afterwards? I would choose that decision.