Why would they ask all these questions? Her right of access depends on confirming her family relation to you. For a stay longer then 3 months, her residency depends on you being able to be self sufficient, you must have enough income. If she has an income, great but it shouldn't matter. Your chat history shouldn't either... the authorities would simply need to confirm that:

1) you and her are family
2) she is going to join you, or travel with you to the UK
3) you are both who you say you are, no fraud etc.
4) There should (is!) be no need (requirement!) for showing financial solvability, insurance, accomodation etc. Only after 3 months (residency), you being selfsufficient.

More info:
- http://europa.eu/youreurope/citizens...y/index_en.htm
- http://europa.eu/youreurope/citizens...e/index_en.htm
- http://eur-lex.europa.eu/LexUriServ/...77:0123:en:PDF