Saying no
None of this is expert advice. It's what people worked out for themselves, usually the hard way — what actually helped, and what they'd tell someone standing where you are. Take what fits and leave the rest.
Focus first on stopping the payment for meals rather than gestures like opening doors.
Paying explicitly costs money and is more egregious because it involves money and countermands your actions and intentions.
2 people, independently
State that a request is not possible without providing a reason.
Explaining the reasoning invites arguments about why it cannot be done.
one person who lived it
Resist the urge to elaborate on your refusal after delivering it.
Elaboration provides points for the other person to argue against.
one person who lived it
Immediately offer an alternative resource or person to contact after declining.
Suggesting a path forward redirects energy and removes the reason to argue.
one person who lived it
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State clearly that you are uncomfortable with the situation to avoid misinterpretation.
Indirect communication can be misinterpreted as permission to continue.
one person who lived it
Intentionally refuse to offer explanations for why you are uncomfortable.
Offering explanation invites discussion, debate, or counter-points.
one person who lived it
Accept that if your decline causes problems for the student, it is the department's responsibility to resolve them.
one person who lived it
Use impersonal reasons for declining, such as lack of prior interaction or mismatched interests.
one person who lived it