Just one plus... The recommended weight gain for pregnancy is 25-30 lbs. During first trimester, some women may gain some 2-4 lbs, others none, still others may actualy lose some due to v/n etc. As pregnancy progresses, mom's caloric intake increases, maybe 400-500 cal extra daily at end of pregnancy...But not for 2. F/u with doc regular and follow the OB advice for proper diet/wt gain. Good luck.
U can but should u? A woman needs to nourish herself and her fetus (es) when pregnant. It is probably best for her to speak with an experienced OB or nutritionist about what is best to eat when pregnant. I will add my guide to healthy eating in the comments below the answer for more information.
Baby very small. The answer is yes, but I always tell my patients "you eat for two, but remember the baby eats very little because its very small :)".