With 401ks, if you're still working and contributing to the same 401k, you can skip the RMDs until you stop working. If you have old 401ks hanging around, you have to take those RMDs. Five percent owners have to begin RMDs, although they can still contribute. Are 403b rules different? I'm sure they are, because this whole area is so #%@ complicated with different mandates for plans that are essentially the same thing.
In your case, though, the client is not contributing to her old plan so must begin RMDs. She may not want to wait until April 1 following the year she turned 70 1/2. She will be required to take two distributions that year, one by April 1 and the next by Dec 31 (the RMD for that year). This might bump up her tax bracket, raise her Medicare premiums, reduce allowable deductions, etc. I agree with Pacun that she should take the distribution and put the max into a Roth.