In your Vishnu Sahasranamam, you have mentioned about the particular star and chant the relevant namam for 11 times.

Answer: You can convince her the benefits she could get by chanting the same. You can, word by word split and teach her the entire stanza for a week to learn. Interest plus iniative can make wonders in ones life. So, I suggest you take the iniative to get her interested in the subject. If one person is suffering from any illness and the doctor recommends some medicine, can the other sibling take the medicine instead, because the sufferer has some problem in taking the medicine? If you know her Nakshatra Padam, then it is only a two line slokha she is to ricite; if the charan i.e. padam is not known, then it is just only eight lines of the slokha in Sri Vishnu sahasranamam numbering from 85 to 88 to be recited. It might take few days to memorize these two stanzas. The best recommended method is, for her to listen the entire Sahasranam couplets for few days.