Glass bowl safe in pressure cooker?

Assuming that you are talking about a tempered glass bowl that is marketed as microwave, dishwasher and oven safe, there should be no problem in the pressure cooker. For glass vessels, the most critical uses are rapid temperature changes and uneven heating, the surrounding pressure isn’t an issue.

I recommend the following safety measures:

• Before every use, independent of cooking method, check for (hidden) cracks with a quick visual inspection and by lightly tapping it with your knuckle or fingernail. You can hear hidden cracks. Don’t use a damaged bowl for anything involving heat, cold or temperature swings, ideally discard it entirely.
• Don’t place the glass directly on the pot’s bottom, use a wire trivet, steamer insert or other support.
• Don’t seal the container, if you want to cover it (e.g. to prevent condensation from the water in the cooker), use a loose lid (not the plastic lids that come with the oven-to-fridge storage containers), a plate, or tent with foil.

I just used one Anchor Hocking glass bowl covered with foil, for a shrimp recipe on top of the trivet, and it cracked in half. :-( Big disappointment.