On a side note before I give you my recommended procedure: Please switch to another pellet brand---the fruit Zupreem are poor in fat, have many cheap allergy-inducing ingredients, high in sugar and have a lot of artificial colours and preservatives--this is NOT something you want. If you cannot/will not switch over then please put your lovebird on the natural Zupreem pellets, they've no artificial colours and less sugar.
Now---there is NO reason your bird needs to have food available 24/7. As you've observed (and the same is true in humans) that constant snacking and always having tastier but less nutritious fare around results in poor eating habits.
She picks out the seeds because they're familiar, taste better and she likes them. She's not going to eat pellets if she's not hungry and she knows there's gonna be tasty snackables all day.
SO--first step is to see how much your bird actually needs to eat in a day (offer her a dish of seeds etc in the morning and weight it before and after/give her a trial amount say 3 teaspoons and add/subtract till there's no leftovers but she's maintaining weight/body condition).
Second step is to split that amount into two meals---breakfast and supper. Don't leave the food down for more than an hour or two--it could spoil and she'll only pick at it because she thinks its gonna be there all day if you do.
Third step is to figure out your percentages. Say you want to feed 50% pellets and 50% percent veggies/fruits---and you know your little lovebird eats 4 teaspoons a day. SO in order to get what you want she gets two teaspoons of pellets in the morning and 2 teaspoons of veggies/fruits at night. Of course these are rough percentages but it helps.
Its very important to weigh her daily and make sure she's not losing weight or body condition---but don't be afraid to let her go hungry and miss a meal either if she throws a fit and doesn't want to eat. They're usually hungriest in the morning so offer the least preferred meal as breakfast.
Good luck
