Vit D does yes, comes from light (UVA/UVB i'm not sure which one) and it is required for calcium to be absorbed BUT lighting isn't required if you provide vit D in their diet ie. calcium with vit D or vitamins with it. I use reptical with vit D and have never had a problem.
Could you please clarify what symptoms your vet described resulting in him diagnosing a calcium diffencecy? Does she have bent legs or a larger lower jaw, any physical signs? Simply not eating isn't a reason and most geckos, including mine, have reduced their eating to almost nil due to the colder weather. Although it hasn't happened with my girls yet, leos can develope eggs without mating, and this yes could be sucking the calcium from her. Do you provide her with a dish of calcium in her enclosure all the time?
As was said by others, forcing your gecko could result in more harm than good and i'm rather upset that a vet would suggest such a thing without giving proper instructions on how to go about it!!! I'm also not impressed that he would instruct you to remove her hiding areas and force calcium on her when its a lack of vit D that will cause the calcium not to be absorbed. Simply adding more calcium isn't going to correct the problem if she isn't getting vit D. Not having a place to hide is going to stress her out and make her worse. Did he ask about anything else other than UV light? Is she in a high traffic area where passerbys might be scaring her, hows her temps, was she checked for parasites,what are you using for substrate-is there a chance she's impacted if your using a loose substrate? When she does eat what does her poop look like, normal? All these things could add up to a gecko not eating.
There are many pics of gravid female leos that have been posted. I'm sure you'll come up with tons of them if you do a search. I'm pretty sure theres been a few recently so you could also just scan through the posts for the last month.
Sorry this was so long....I hope your gecko does well 
Red 
>>Recently I have been having problems with my four year old female leopard gecko not eating, so I took her to the vet. He said she has a calsium diffeciency, from a lack of UV. She also may be trying to lay eggs, which might be sucking up the calsium. He said to give him a call if she develops 2 bumps. I can't tell, any info or pictures on this would help. Thank you for your time.
>>
>>Lisa
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Crested Gecko Zeek:1.0
LEOS: Boo: 1.0 normal , Bronx & Nala: 1.1 blizzard,
Lily: 0.1 patternless, Abby: 0.1 albino, Zoe: 0.1 reduced pattern, Dot: 0.1 hypo
Chip: 1.0 papillion (small dog)