Do you want to show her she's the first and most important person to you? Maybe you should consider dating your lover, y'know exclusively and not as some secret casual affair.

Have a fresh start, date as if you never dated her before, ask her out on a date to some restaurant you both haven't been to, get to know her again. Be serious about it, no cheating, no keeping it secret, no lies, do all the sappy romantic stuff like picnics, flowers, handholding, walks on the beach, dinners at restaurants just be a regular couple.