You must have understood by now that having great Love and Relationships is not an easy thing.
Love is actually not an emotion, or a need, its a state of consciousness. Love just flows in absence of fear, anger, greed, insecurity etc.
So if we can somehow let go of fear, we can easily experience Love and Compassion. You can certainly do things that will make her feel better and make her feel that you care for her but there is no limit to do this. One day you’ll do things for her and then she’ll be happy then next day you have to go out with friends and that will make her feel unloved and insecure.
You both need to manage your personal needs and desires. Once you both start feeling happy and contented, Relationship can grow. Once you are happy about Life the way it is, at that point Love becomes truly unconditional.
You both need to heal and gain a healthy state of mind and body. Take up a daily physical exercise routine and pranayama/meditations can all be helpful here. Only healthy people can experience beauty of Love.
You can let her know that it broke your heart when she was telling abt the other guy and that you still feel something for her. Go out on a vacation or at a fun spot, share some beautiful times again and rest should be fine.
But the key point for long term happiness is – manage your needs and desires. You don’t want to depend on a single person to fulfill your needs.