It is rude to show up on someone's doortstep without notice or invitation and expect to be hosted, especially with multiple additional people.
The rudeness is compounded if you have already been informed that the homeowner does not welcome drop-ins and elect to stomp all over that boundary anyway.
That said, OP, your mistake here was that - instead of sticking to your previously stated boundary, refusing the visit and being (kindly) clear why - you assumed the role of host to an uninvited, unannounced, unwelcome visitor and proceeded to perform your duties begrudgingly and resentfully.
"I'm afraid we're not available today, Martha. Perhaps next Saturday?"
"What a pity you didn't call ahead; today isn't a good day for a drop-in visit. Please call next time so that we can avoid these disappointments."
"We're not available/just on our way out."
"Martha, I enjoy your company/value your friendship (if true), but I need you to respect that I don't enjoy drop-in visits/find them disruptive/whatever. Please call next time if you want to spend time together."
This is clearly a person who requires more explicit communication than what you've been giving.
...The thing is OP, once you have accepted the role of host (by not turning unasked-for guests away), there are certain broad expectations.
Yes, you are absolutely entitled to set certain limits on the nature/extent of your hosting - you certainly don't have to host anyone who bullied you into it or barged their way onto your property, and you don't have to run yourself ragged catering to four uninvited guests every precise whim.
...But you are obliged to conform to at least certain minimal norms, like letting them into your house, providing shelter, food/water and amenities.
If you don't, you can expect your (now guest) to feel varying degrees of slighted/hurt, and you can expect to alienate anyone else who makes overtures of friendship.
Far simpler and less dramatic and upsetting to either refuse unannounced drop-ins or require guests to wait to be invited, no?