Even if you were to sit and watch your geckos for 14 hours a day, (and I'm sure you don't), there'd still be a window of 10 hours when she could be eating the calcium right out of the bowl. They only need a few licks, which only takes a few seconds, and which is why you'll never notice a change in the amount of calcium powder in the bowl.
So, if she needs it, and she probably does due to the fact that she's gravid, I can virtually guarantee you that she's licking up the powder. Their natural instinct tells them to find what their body needs.
Ways to ensure that she's doing so include putting the container with the powder somewhere close to her favorite hide, and making sure that its the only powder substance she has access to (ie: no sand or loose substrate).
As for liquid calcium, if you chose to do so, and you probably don't have to IMHO, you can just mix up some calcium powder with water and drop a drop or two on her nose.
Just as a side note, I've been keeping and breeding leos for 3 years and have probably actually seen a leo licking up calcium 10 times at the most ... and that's all of my leos, including many babies over 3 years.
Hope this helps,
Joel
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2.5 Leopard Geckos
0.1 Ball Python
0.1 Okeetee Corn Snake
1.0 Blair's Phase Gray Banded Kingsnake
0.0.2 Crested Geckos
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