Is it her, me or the MS?

Connected recently with a long ago friend only to learn she is dealing with MS. We have had really good correspondence catching up on each others lives, careers, children, etc. My mother had ALS so I have some experience front row and center supporting someone with a debilitating neuoroligic condition. I have been very positive and supportive which she has welcomed with open arms with plans to continue to be a source of positivity. Practically in mid conversation it stopped--after two unreturned e-mails I don't know what to think. I have reread all our messages for any hints--there are none. Is it possible that MS is the reason? Any insight into this would be greatly appreciated. I'm left baffled, confused and helpless as what to do next--if anything. Thank you in advance for your help.