Dear Starlight Glimmer,
Thy nerves are not without reason. Time has passed, and a point is being reached on whether or not thou should commit to being in a true relationship. Tisn't a bond set in stone, by no means, but it is a commitment nonetheless that requires deliberate intent and an allocation of energy. In being so committed to Sunburst, thou art making a promise of sorts to prioritize him and his needs. This is a mutual commitment, Starlight. In the same way thou would treasure him, he would treasure thee.
Thou must search thy heart and challenge the depth of thy feelings. Thou hast given the stallion a chance. Has his courtship pleased thee? Thou hast admitted as much. But dost thou simply adore the attention? For this alone is not sufficient to be his new partner in romance.
The feelings must be moving and growing in the same direction, even if they are not quite of the same magnitude. This is often the case in romance, Starlight. Do not be dismayed if Sunburst's feelings seem deeper than thine. It is possible that thou could come to care for him in equal measure. For now, evaluate only if thy affection is growing, and could grow further still.
I must state that there is another side to this. That perhaps, thy feelings do not blossom but remain a closed bud. Such was the case for this princess generations ago before Discord ravaged our land with his mad magic. A mare of my Night Court made plain her affection for me. This was during a time when such romances were quite frowned upon, for I was royalty and she but a servant. Starved for attention and already barreling toward my lonely fate on the moon, I fanned her fancy until it raged like wildfire-- not because I truly returned her feelings, but simply because I basked in the love-sick worship she lavished upon me. I neglected her, dear Starlight, and she suffered greatly. My sister, never one to let ponies suffer in her orbit, took the servant mare aside. Their palaver was long, and Celestia's patience was unyielding. She broke through to that poor mare, and with her help, she found a new station as a lady-in-waiting for a noblemare in Prance. Oh, the tantrum I threw! My toy had been taken away from me.
Starlight, I know very well that thou art nowhere near as cruel and as callous as I was then... But I must warn thee that should ye judge thy feelings poorly, or perhaps hope vainly for them to grow when there lacks even seed to germinate, Sunburst may suffer in a similar fashion as my mistreated servant. In such an instance, though it may pain you some and him more, t'would be a kindness to end the courtship before it can advance further.
If these thoughts dampen thy spirits, then set them aside for now, Starlight. Enjoy thy time with Sunburst. I trust that thou willst do right when the time comes.
Sincerely,
Princess Luna