Yes her & Susan Battersby did commit minor cheque book fraud once. Smuggling cannabis. I thought she just dealt with it at Goldsmiths college. Although I've never seen a source.
Neither of those crimes relate to the massacre. However Bamber's caravan break in does.
Anyway, there is no possibility of a 21 year old woman doing her second degree trying to frame an innocent man of killing his family. A month after the massacre. On the assumption she was jilted, devastated, mad & savagely vindictive in the first place.
There are too many huge & obvious disadvantages.
It might be balancing one set of disadvantages against another .
Career ruined , criminal charges , perhaps being accused of perverting the course of justice , perhaps being accused of being an accessory , versus a clean slate and being hailed a heroine for helping to jail a suspected child killer.
If you are going to hypothesise you should consider both angles .