Difficult 2 Answer. Size of penis is not a detriment to good sexual satisfaction to either partner. Some women may prefer a "smaller" penis as some may prefer a "larger" penis. If you and your partner are dissatisfied with your sexual intimacy/relationship over the size of the penis, perhaps you need some counselling, new technique or maybe the relationship is just not going to work out.
Probably. Some women will break up with a man for any excuse.
Maturity. Though we all have specifics in our sexual desires; and even though penis size is the source of much joking and anguish; in a good, mature relationship, physicality and its quirks takes a back set to compassion, character, depth. As drs have noted, sexual satisfaction for both men and women need not be related to obvious physical traits--intimate communication is the most arousing thing there is.