Maryh,
Did your mom have a bone marrow biopsy? That's the usual way to determine a diagnosis of MDS.
Every MDS treatment has risks, so "wait and watch" isn't necessarily the wrong tactic, especially for someone in their 70s. If you aren't confident in her doctor's advice, you could encourage her to get a second opinion.
I assume that your mom will have regular CBC (complete blood count) tests to watch for changes in her platelets or other counts. She can ask for copies of the results, and you can follow her counts over time.
I don't know you and your mom of course, but I know that some people want to shield their family members, even their adult children, from a frightening diagnosis, so she may be more concerned than she lets on. Every family has its own dynamics, but I hope she'll accept your help and understand your justifiable concern. For example, if you share what you learn about living with low platelets, I hope she'll follow your advice.
You and your mom should both read the free materials about MDS that you can get from the
Aplastic Anemia & MDS International Foundation. You might also consider whether you and/or she should attend the
Patient & Family Conference coming up in July in Indiana. There you'd be able to meet other patients and hear from MDS experts in person.