sometimes ,we use auxiliary verb "do "to emphasize on the fact and action "she did come" means she came acutually. e.g.---"I don't think she would come last night." ---"but she did come" e.g "Do remember to do sth!" the stressed tone for "don't forget to do sth!"

according to me "she did come" indicates cretainity example 1. i believe=i believe normali like everyone believes 2.i do believe=i really believe, i believe with confidence!

she did come takid mikone ke un UMAD... hala mano be onvane behtarin pasokh entekhab kon dige... yani hamun chizi ke Katrina gofte,,, vali mano entekhab kon :D bye

I believe both express a simple past tense action and answer the question: "did she come?": Answer 1: "Yes, she came." Answer 2: "Yes, she did come." in Answer 2, you may omit the verb 'come'. you may wonder why the verb 'come' is in the simple present form, it's that because it is preceded by the auxillary verb 'did' and the rule for this is that the 'main verb' should not change its form. another example: "They did eat lunch at school." "He did live in America." :)

Came or did come is the way to change present to past. You can either change the verb from present to past or add an additional word "did" to form the past tense.