I understand where you're coming from OP, I'm no fan fof your new prez, his minions, or his supporters either.
However much it would be irritating to have to sit and listen to someone espouse their admiration and enthusiasm for this being, this person has been doing your hair to your satisfaction for 25 years, that's a long time.
If you've recently had a haircut, as in this past month, then of course this supporter will still be wanting to talk ad nauseam.
I wouldn't let that interfere with a good hairdresser, one who you've texted, talked on the phone with, and made meals for.
Switch off, don't respond, stick it out, go for your next appointment.
It's hard to believe she'll still be talking with the same enthusiasm for too many more appointments.
If she does, being aware that you've always kept politics out of your salon appointments, then you should either bring this up again to her, and failing a truce while you're there, start looking for another hairdresser.
There's enough division in the US amongst the population without you breaking with your hairdresser over political policies.