I searched:

Mary Baker Eddy, by Gillian Gill

Rolling Away the Stone, by Stephen Gottaschalk

God's Perfect Child, by Caroline Fraser

From what I saw, it looks like there were some accusations about Mrs. Eddy being addicted to morphine in mid-life, but not much hard evidence. It is clear that she received morphine injections several times very late in life when she was passing kidney stones or suffereing with what Gill says might have been pnemonia or bronchitis. Frye's diary does mention "the old morphine habit," (diary entry May 9, 1910), but Gill says that his other writings do not suggest addiction.

To see what Gill says, click on the link to Gill's book I provide above. Then click on "Search inside this book" under the book's picture, seach on "morphine," and then click on the links to pages 215, 447, and 545-546.)

Gottschalk has good discussion on the subject on pages 349-353 (as above, just click on the link I provide and then do a search on "morphine." )

A similar search for Fraser's book yields reference to her occasional (not habitual) use of morphine.

I'm giving you these references so you can do some reading for yourself rather than just relying on my summary. The topic has been disputed enough that I'd rather you see what the authors say for themselves.

My own feeling is that, however she may have used morphine earlier in life (keeping in mind that morphine was commonly used in her day), she was not addicted later in life. She did use it upon occasion, though.