I went to the UK for the first time, alone, at 18. My parents were unimpressed, to say the least. Infact, the only reason I was allowed (yes, allowed. oh dad.) was because my older brother (9.5 years older) replied "Well, at her age I already had a kid and was about to get married. Who cares if she wants to go see another country?"
It was hard, and difficult, to go without their real blessing. Eventually they got around to the idea although now they regret it because I moved away.
I understand where you are coming from. Luckily, for me, it all ended up okay. I made a few friends, got married to one, and fell in love with Cambridge. Not to mention my parents finally getting over the idea they could control everything I did. Hopefully, your Mom will come around to the idea. Even if it's not until you're back. Because at least then she'll give her blessing for future trips if she sees you're safe and fine!