Move at the pace of the slower one. Don’t let anyone pressure you. And certainly don’t pressure the other. You want the decision to commit to marriage to come from a clear head.
People process in different ways. People’s schedules are different and they may not have enough quiet time to process what they are feeling and learning about the other person. They may need some time to talk things out with someone – and that person may not be available right away.
If you care about this person and you want a solid relationship, you will have to adjust to their processing style. Even if it frustrating to you. (And those around you).