Whilst I agree with the grans here, I wonder why you have felt that you had to give in.
Parents who are stressed sometimes find that they don't have the energy to insist on every rule that they would like to. You may like to think - and discuss with the other parent, and others involved with your child - what you are going to insist on and enforce, and what you are going to "let go".
Better to have a few rules & strict boundaries than a lot of half-rules that aren't enforced and leave the child confused.
If this is one you want to enforce, you may need to look at what you are doing - are you sitting with the child at table, are others there? Is it a pleasant, social experience? Or are you sitting the child on her own, whilst you get on with something else? Do you have the time & energy to commit to a proper family mealtime?