First, it's important to understand why glasses get stuck: typically it's due to: 1. Vacuum seal formation 2. Microscopic surface adhesion 3. Slight temperature/pressure differences when they were nested

Here are some additional methods to try, in order of increasing complexity/risk:

1. Dish soap and hot water method: - Fill sink with very hot (not boiling) water - Add lots of dish soap - Submerge both containers - Gently twist while pulling apart - The soap can break surface tension and act as lubricant

2. Vibration method: - Tap gently around the rim with a wooden spoon - The vibrations can break microscopic bonds - Combine with dish soap method above

3. Compressed air method: - If there's any gap, try forcing compressed air between them - Can use canned air duster or bike pump with narrow nozzle - Air pressure might help break the seal

4. Expansion/contraction method (more controlled than previous attempts): - Put ice water in inner container - Run hot water ONLY on outer container - Wait 1-2 minutes - Try gentle twisting motion - The differential thermal expansion might help

Important safety notes: - Avoid extreme temperature differences that could crack the glass - Don't use metal tools that could chip the glass - If trying percussion method, be very gentle - Wear gloves in case of breakage

Has she tried any of these specific variations? The key is often in the details of how methods are combined and applied.

Water, soap, oil, compressed air etc will not work. Ask your friend to gently tap around the edges of the container that is stuck with either a wooden spatula or the back of a wooden ladle. Gentle taps in the direction of getting unstuck all around the edge of the stuck container. May require few minutes of tapping.

Source: This has happened to me many times.