hi there so sorry to hear about your mum @soosall I would keep the person with the cold as far away from your mum as possible if you can or can they come another day ? It’s quite possible those that are with the sick relative could also be contagious without symptoms yet too. Chemo can beat the shit out of your immune system and especially for older people and the new chemo regime is slightly better in that regard. Your mum also probably has not had a flu shot either yet so that can make her more susceptible.
If they have to come and see you hand washing hand washing hand washing for everyone especially after blowing their nose etc . It’s the main defence to kill any germs. Also wiping down any surfaces they touch. A mask will help but can be quite claustrophobic and uncomfortable as well.
She could just as easily pick something up out shopping too but I would take extra precautions for sure. Just use Common sense and you’ll be fine Hope this helps. Margie. Xx