Explain to your mom that you’re in a legal age right now, so please allow you to decide on your own, and trust you that you wouldn’t do anything that can disappoint them. Obeying our parents is very very good but we have to insist that we need to be independent because we’re not a child anymore. You have a boyfriend, stable job, and savings, so there’s no reason for them to not allow you to go with that vacation, and promise them that you won’t make them disappointed.