How can tell "refuse" and "reject" ?

Basically Niki, "refuse" implies an offer or request whereas "reject" is a bit more general, a refusal to consider. Hope we'll hear some more subtle diffs

Tes, help

Thank you so much!

You're welcome, Niki; it's the least I can do

But Tes, I'll bet you can elaborate

When you refuse something, you don't accept it.
" The girl refuses to take her medicine"

When you use reject, you not only don't accept something, you flat out don't want to go any further.
" The promotion was rejected by his supervisor"

Reject can also be as noun -
"The dress was a reject and thus much cheaper"

Selectmytutor needs to stop responding to English language learners' threads, as "she" is obviously not a native speaker of English.