Yes, it's OK to skip a meal

If the puppy is hungry, then she'll eat well at the next meal. And if she doesn't, it's a pretty good clue that she's really not that hungry at all.
Young puppies are notoriously "picky". But you know, most of the time they're not really being picky at all (unless they're taught to be). It's just that they grow in spurts and during a growth spurt their little bodies need all the energy they can get. So the pup has a good appetite and eats well. Then the growth spurt stops, and the pup has no need of all that energy - and their appetite goes down accordingly. That lasts two or three weeks, then the next growth spurts starts.
Now what very often happens at this point is that the owner gets worried about the pup not eating much, and brings out all the enticing extras to try to tempt the pup (who simply isn't hungry). If you keep doing that, then the pup will learn not to eat until you produce something extra-tasty

And all during a time when the pup really didn't need the food and was actually just responding to her body's needs when she just picked at her food.
So, it's actually better to simply accept that there are going to be periods that your puppy has little appetite and won't eat a lot. Those will be followed by periods when she eats everything in sight. Then isn't hungry again. By around 4-5 months, the big spurts of growth are all over and things will even out - but until then, it really is better to let her just respond to her body's needs and don't try
too much to tempt her to eat when she doesn't want to. Bringing out the yummy extras every time she doesn't want to eat will actually teach her to refuse her food until something extra-special arrives.