es geht ihr gut she feels well i do not understand it
es geht gut translates as it goes good or it goes well. Therefore 'es geht x gut' means 'it goes x well' or 'it goes well with x'. For x you can fill in for example: mir (me), dir (your), ihm (him), ihr (her), uns (us), ihnen (them). For x you can also fill in words such as meinem Betrieb (my company), meinem Land (my country), meiner Familie (my family) meiner Frau (my wife) etc.
I'm not sure what exactly you don't understand.
The phrase "mir (ihr or any other pronoun) geht es gut" is mostly used like answer on question "Wie geht es dir? (Ihnen, usw.) which means how are you? (or how is she and so on).
The question literally means how is it going by you (and you ask the other person how is his/ her life going)
i would sentence "She feels well" translate more like sie fühlt sich gut and use it to ask someone how he feels when he/ she is sick.