My mom has been petitioned by her sister and she is set to go for a consular interview. she was supposed to go with my dad but my dad unfortunately has to be treated for a medical condition and the treatment would last for 6-8 mos. before he can be medically cleared.

My question is:
Is it ok for my mom to go to the US ahead of my dad? She is planning to join us next month.

Will my dad have any issues particularly in the consular interview/processing after being cleared medically, considering my mom who is the principal/benificiary of the GC will go ahead of him?

Thanks!