My gray cat is very lovelybut I cant pet her unless I'm talking to her but will only let me pet her for a little bit of time but will strangely let me play with her kittens I want to pet her for a longer time and not have to talk to her to pet her what do I do

My gray cat is very lovely but I can't pet her unless I'm talking to her. She will only let me pet her for a little bit of time but will strangely let me play with her kittens. I want to pet her for a longer time and not have to talk to her to pet her. What should I do?