Assess the risk of her exposure to feline distemper:
Does she go outdoors?
Do you have any cats or other animals which go outdoors and come back inside without being scrubbed down immediately?
Do you or anyone in the household handle cats from outside the home?
If you answer yes to 1 or more of the above, those put your cat at risk.
If you, household members, or guests do handle cats from outside the home, are they vaccinated?
If you, household members, or guests handle cats from outside the home, upon returning to the home, do you immediately strip all clothing (including any coat, scarf, gloves, boots, etc) and put them in the wash or disinfect them, and take a bath, plus wash your hair? (Doing so reduces the risk from fomites - ie infection-contaminated clothing and body)
Are all pans used to feed the strays brought inside and IMMEDIATELY placed in a dishwasher or disinfecting solution and washed?
If you answer no to either question above, those put your cat at risk.
So - how're you doing with those questions? Does that help clarify what you want to do?
Some of the risks you can reduce, some you cannot control - like guests to the house.