Most Helpful Guy
First off, I think there is too much pressure in general on women, particularly younger women, to be thin.
Second, as other posters have mentioned, it is how you carry your weight that matters. Just speaking health wise, I would not advise you to diet down from you are already. You are tall and 145 lbs is perfectly fine for a woman who is 5'10"; I'd say that 135 lbs at that height is too thin. Exercise to keep yourself firm, tone, and healthy is good, but scales are overrated and you should not use your weight as a way to judge how you look.
Bottom line, if you feel good and healthy at your present weight, then don't stress over the number.