I'm very sorry for your loss.
I think your tattoo looks great, and the size is perfect for your arm. I get the impression you feel it doesn't do your mum justice? Nothing will ever truly compare to her, after all, she was your mum :) but how about seeing your (lovely) tattoo as a starting point?
Did your mum have any particular hobbies or interests, or things/people/pets that meant a lot to her? how about maybe incorporating some ideas into a sleeve and build those around your original tattoo. You could also have fun with it too, by adding little things that just you and your family would understand, but if anyone asked you could explain and then talk about the things your mum loved and enjoyed. If you take your time, I'm sure you could find a fantastic artist who could gradually bring it all together for you.
I have been down the laser route, it was painful, bloody, sore and expensive, I also have a bit of scaring, and its still not gone :( I too went in head first and spent two weeks crying and obsessing over my first tattoo (mine is a genuine disaster zone , unlike yours!) I then spent the next ten years constantly wearing long sleeved shirts, even in the summer. That was it for me, longsleeves4life!... until last Wednesday when I went to a brilliant artist and he made a start on what will be a full sleeve tribute to my pets! and something will be done with that mess on my arm but I'm not sure what yet ;)
It's a long story as to why I got out of my tattoo rut, but the point is, your tattoo is actually good!!! it really is, I think to laser it would be a waste, get planning on some ideas to go with it, enjoy seeing it all come together, have fun with it, research artists and turn it into everything you want it to be.