AVG is fine. I'm not sure if she was trying to run Ashampoo with Defender but two real time programs can conflict.
I run the Defender antispyware (comes with Vista) Avast free anti virus and the Vista firewall which are all fine.
Scanners like spybot are fine but do ensure they are the Vista compliant versions. Superantispyware free is very good with Vista as a scanner. click here