Hmmmm, it seems cards on the table face up is needed, as my mum used to say "Its not what you say but how you say it.* If i were you i would go see you MIL, not via text or WhatsApp because electronic messages can be soooooo misleading.
Could you go see her and explain your concerns, cards on the table and all that.
You're going to get a far better reasoning to it all than just going by electronic messaging.
Thinking of you ... hope all turns out okay.
What is a reasonable minimum spend for an online grocery delivery??