Wearing other people's glasses will not harm your eyes, but consider this:
1. You do not really know why your vision is getting blurry. There could be reasons other than spectacle power, so you should still get your eyes checked out to avoid delayed treatment of eye conditions
2. Even if your aunt's glasses make your vision clearer, it is all a bit of a hit and miss. For young people, overpowered shortsighted glasses (overminusing) often make vision seem clearer, but the strain on the ciliary muscles to constantly accommodate could cause brow aches and intermittent blurring.
So all in all, it is not advisable to wear other people's glasses, except in situations where there are no other choices and for limited periods of time only.