She can't OR she WON'T!

Today was our 2nd visit with Baby Love's g-ma.  Last week I left her with a 2 oz bottle and her feeding pump, tube and supplies. When I went to pick her up after the visit I expected her to have eaten about 30 ml's from the bottle and 35 ml's from the pump.  The dr's orders are to feed her from the bottle ONLY until she tires (around 20-30 ml's) THEN put the rest on a tube feed.  G-ma either can't or won't use the pump BUT she won't admit she doesn't know what she's doing!! Baby Love is burning too many calories drinking from the bottle but they don't want her to lose her desire or ability to suck.  Today, after the 2 hour visit, she told me again that the baby finished all of the bottle.  I already told the agency worker...now I have to figure out how to explain to g-ma what she's doing wrong!