I'm so sorry you and your cats had to go through so much, due to your move and Mamacita ran away due to the negligence of others. Hopefully she will find you (by scent), if it's not too far away, or another kind person will feed her outside their home.
Re: your main question--even though you feel Boo may feel more secure if she had a companion, in general, older cats are just bothered by the antics of young, energetic kittens. Because she's still afraid and adapting to her new environment, I wouldn't make any big changes at this time, like getting a new kitten, but try to help her overcome her fear of the new place. Get some Feliway plug in diffusers, which emit cat calming pheromones to help with stress. Humans can't smell them.
There are other over the counter calming remedies. One is Rescue Remedy Pet and the other is Composure chews/treats. They are available in your pet supply stores. One note: don't give BOTH the Rescue Remedy Pet and the Composure treats; choose one and give that, only. Either one can be given along with the use of Feliway, which is not ingested.
Also, make sure she has a tall kitty condo or cat tree to play on and get her some new toys which will intrigue her. Continue to give her TLC, but don't push her if she is still scared. Try to run a white noise machine to cancel out the outside and inside noises that are scaring her.
I hope all will be well!
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