Welcome to the forum!
It's always nice to welcome a fellow Jackson's cham keeper

You are very wise for asking questions here.
You do really need to know what the temperature is in her basking spot and in the rest of the enclosure to be sure what is going on and to ensure that her temps are ideal.
Jackson's need much cooler temps and higher humidity to stay healthy than Veiled, Panther and many other chams do.
Please read this excellent Jackson's caresheet for more care details:
https://www.chameleonforums.com/care/caresheets/jacksons/
The more varied her diet is and the better nutition her feeders get, the better her nutrition will be.
Please read this for more info:
https://www.chameleonforums.com/care/food/
In addition to a well fed variety of feeders, I lightly dusted most of my pregnant Jackson's feeders with calcium
without D3, unless they were already a calcium-rich feeder like Phoenixworms or silkworms.
Her feeders were also dusted 1x a month with Reptivite multivitamin without D3 and 1x a month with calcium with D3.
Overdoing supplement dustings is known to be harmful to Jackson's and other montane type chams.
Calcium without D3 is the most frequently used dust and is more difficult to overdo than the multivitamin and calcium with D3 are.
Gaping can indicate overheating, breathing issues or is used to scare you away when a cham feels threatened.
Jackson's are most often rather shy and pregnancy will make even a trusting female much more wary of people.
She knows that she is more vulnerable and perhaps feels the need to protect her unborn babies.
Hands off, while a good policy for non-pregnant females, is even more important for a pregnant female.
The less stress she deals with, the better.
Typically, a female will eat much less or stop eating as she nears giving birth.
Unlike many other chams, Jackson's females give birth to live babies instead of laying eggs.
My female moved around her cage a lot the day before giving birth and she gaped repeatedly during the morning she was "in labor".
Generally, the babies are born before Noon.
Baby Jackson's are tinier than you may think---about the size of a cricket and not much different in color.
They need to be carefully removed to their own enclosure as soon as they are found.
Momma will eventually get hungry and the babies are cricket size.
You can also read this thread and others for ideas on how to care for the babies:
https://www.chameleonforums.com/newbie-need-info-neonate-jacksons-chameleon-care-115059/
You'll want to have everything on hand in advance, since it will lessen the stress on you when the babies are born.
The number of babies usually ranges between 10 and 30, with around 20 being quite common.