Download https://www.dropbox.com/s/dwydyfiwayzr5ox/patch.rpy. Place it in the game folder within the My Lady folder. (To find it, right-click the game in the Steam client, then go to Properties -> Local Files -> Browse Local Files.)

This mod slightly increases the font size to make the game easier to read.

Open patch.rpy in a text editor.

You can increase or decrease the font size by changing the number after style.default.size = to whatever you want.

You can also change the font by adding a different font file to the game folder, then changing the line style.default.font = "POORICH.TTF" to style.default.font = "YOUR_FONT_FILE_NAME".

If you don't like the way the font mod looks, just delete patch.rpy and patch.rpyc from the game folder.