This is a high maintenance person. The Free Dictionary defines a HMP as
informal (of a person) requiring a high level of care and attention;
The Urban Dictionary, which is an appropriate dictionary for this phrase says:
Has higher than normal expectations; has a greater requirement for
affection or attention; has more needs and/or demands and therefore
more difficult or challenging. Doesn't equate to money or material
possessions alone but may be needy in emotional attention and
affection;picky, bratty, likes things her way, takes pride in her
appearance, finicky. Usually very well put together and usually
independent therefore requiring a lot out of a man to keep up with her.
"If you have to reassure her through texts email or calls that you're
lucky to have her, she's so pretty, etc...- she's a high maintenance
My own definition of a high maintenance person is one for whom you have spend a great deal of time, creativity and emotional energy not merely to keep her happy, but just to keep her not too obviously unhappy.
Say you are walking with her in the rain and encounter a mud puddle. You go into Sir Walter Rahleigh mode and spread your coat over the puddle. She will step on the coat, complain that you should have picked a better route, expect you to produce shoe polish of the right color immediately and be irritated that the color of your coat did not work well with the color of her shoes.
How does she get away with it? She can be amusing enough to induce amnesia until the next time.