It will get better I assure you. I am a non-adventurous chick who first saw snow and hopped on a board at the age of 30. First day I cried on the slope. Now 5 years later I am hooked, I love it.
First things you must do, absolutely if not already - helmet, wristguards and knee protectors. Not expensive, don't go all high-end and flash names, you should be able to get all that for 100 bucks or less. You'll lose the knee protectors after a while (the cheapest and best are the volleyball type ones, you don't need hard shell), I found after about 3 weeks I stopped falling on my front and tended to skid on my bum.
I am also 5'3 (130 lb) and I started on a 148cm board. Now I am on 144cm and I find it MUCH easier. Prob the board is a wee bit big but it won't be the dealbreaker, you can upgrade in a couple years. Changing to a rocker also made a big difference - it vastly reduces the edge-catching.
Finally, practise, practise, practise. Go for shorter sessions more frequently eg 3 hours as then you're not going to be too tired, tired causes mistakes and falls. Don't compare yourself to the boys - we girls are naturally more cautious, you'll improve your speed after you have got the basics down. Keep us up to date on your progress!