I think you are talking about WIDLAY - What I Don't Like About You.
This is the episode where Hannah comes home from filming Indiana Johannie and discovers Lilly and Oliver are dating. She asks questions about how they got together and this causes an arguement to break out.
The episode can be found here:
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link and
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I am not entirely show which episode Hannah starred on a tv show...I think it could be Jake...Another Piece of my Heart which is when she believes Jake and Traci are getting married but they are actually pranking Hannah for the show 'Gotcha'.
The episode can be found here:
link,
link and
link