Siman 79
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א רְפוּאָתָהּ כֵּיצַד, לָקְתָה, חַיָּב לְרַפּאוֹתָהּ, בֵּין רְפוּאָה שֶׁיֵּשׁ לָהּ קִצְבָה בֵּין רְפוּאָה שֶׁאֵין לָהּ קִצְבָה; אֲבָל אַלְמְנָתוֹ אֵינָהּ מִתְרַפֵּאת מִנְּכָסָיו, אֶלָּא בִּרְפוּאָה שֶׁאֵין לָהּ קִצְבָה, שֶׁהִיא דּוֹמָה לִמְזוֹנוֹת:
1 How is he required to pay for her healing? If she became ill, he must heal her (pay her medical costs), whether healing that has a determinate cost or an indeterminate cost. But his widow is not healed from his estate except for healing which has no determinate cost, which is similar to food [payments].
ב רָצוּ הַיּוֹרְשִׁין לִקְצֹב עִם הָרוֹפֵא, כְּדֵי שֶׁיִּהְיֶה לָהּ קִצְבָה וְיִפָּטְרוּ מִמֶּנָּה, הָרְשׁוּת בְּיָדָם:
2 If the heirs wish to specify a cost with the doctor, such that [her healing] will have a determinate cost and they will be relieved of payment, they are permitted to do so.
ג אִם רָאָה הַבַּעַל שֶׁהַחֹלִי אָרֹךְ, יָכוֹל לוֹמַר לָהּ: הֲרֵי כְּתֻבָּתֵךְ מֻנַּחַת, אוֹ רַפְּאִי עַצְמֵךְ מִכְּתֻבָּתֵךְ אוֹ הֲרֵינִי מְגָרְשֵׁךְ וְנוֹתֵן כְּתֻבָּה; וְאֵין רָאוּי לַעֲשׂוֹת כֵּן מִפְּנֵי דֶּרֶךְ אֶרֶץ:
3 If a woman contracts a lasting disease, he is able to say to her that the ketuba can be assumed if she heals herself or the ketuba can be absolved and give her the ketuba, but this is not proper behavior because it is not derech eretz.