At 15 wks he should really have had her vaccinations,and no humans cannot catch catflu,if she's not displayed any symptoms and i'm assuming she hasn't else you would've had some signs ie her not being,seeming to be well,try not to worry yourself Vikki,even if she did have catflu it can be lived with by her,it's not always fatal,it's just when you don't know too much about it and always hearing/reading you tend to remember all the fatal sufferers/stories,but for you and your girlif it's not a problem then don't think about it
Also as you are new to being slave top a kitty,if you haven't got a vet already,please register with one and just have her vet checked,your vet will check her for fleas,worms and make sure alls as it should be and also give you a few helpful hints for you and she to enjoy each other
As when she gets a bit older she will need to be spayed so she can't have babies(don't let her out or near other boy cats as she may get pregnant-even at this age),if you don't get her spayed she could spray wee around and in your home to attract other boy cats