Adult male Hermann tortoises tend to be smaller than females, so the size difference is not abnormal. As long as your more reclined eater is getting enough food, and the other one not getting too much, this shouldn't be a problem. Your male doesn't sound deprived of food, so perhaps the problem would be not giving Tiffany too much food. One thing to look out for is pyramiding, if Tiffany's shell is starting to develop pyramidine bulges on separate scutes then you have a problem and should feed her less often.The diet you're giving sounds great, so if pyramiding is to occur, it's probably from the quantity of food. A smooth hard shell is a sign of a healthy diet fed in appropriate amounts.

Feeding her less often is not cruel, if anything it's appropriate, she might not want to pass a chance to eat and so she's prone to eating too much. If indeed, she's eating too much and/or your male is eating too little, all you should do is to get any small, preferably screened container, place it in the enclosure when it's feeding time, and put one tortoise in. Then you can partition the food into the container and out of it to each tortoise. I would still do that on a few days of the week, not all, to keep the tortoises used to each other when feeding, and to monitor their behavior for changes. Hope it all turns out well for you and your tortoises.

Adult male Hermann's tortoises tend to be smaller than females, so the size difference is not abnormal. As long as your more reclined eater is getting enough food and the other one not getting too much, this shouldn't be a problem. Your male doesn't sound deprived of food, so perhaps the problem would be not giving Tiffany too much food. One thing to look out for is pyramiding, if Tiffany's shell is starting to develop pyramidal bulges on separate scutes then you have a problem and should feed her less often. The diet you're giving sounds great, so if pyramiding is to occur, it's probably from the quantity of food. A smooth hard shell is a sign of a healthy diet fed in appropriate amounts.

Feeding her less often is not cruel, if anything it's appropriate; she might not want to pass a chance to eat and so she's prone to eating too much. If indeed she's eating too much and/or your male is eating too little, all you should do is to get any small, preferably screened container; place it in the enclosure when it's feeding time and put one tortoise in. Then you can partition the food into the container and out of it to each tortoise. I would still do that on a few days of the week, not all, to keep the tortoises used to each other when feeding and to monitor their behavior for changes. 

Hope it all turns out well for you and your tortoises.