Heather has 3 appearances. The default one you first see her in, a goth chick outfit (blech) and the skimpy outfit.
As far as bugs go, you can put that down to two things. The first is the fact they were using an early version of Source, so I imagine in many ways they were pioneers, finding issues even Valve wasn't aware of at the time. The second is that Troika, in the same way as Obsidian, had the Black Isle disease of overreaching beyond their budget, timeframe, and talent (at least in terms of QC). Utimately that was their downfall.