You can fall in love with this person for several reasons. For example:
These feelings can disappear, but not immediately. It is up to you to decide what you want to do.
If you continue your relationship, decide if you want to tell your partner or not. Telling your partner can be a strong sign that you are choosing your relationship and your partner rather than the other person. It can also hurt your partner’s feelings, lead to distrust or make the relationship more complicated. If it is too difficult to talk with your partner, you can talk about the situation with someone you trust.