Is sending text messages sufficient to maintain kinship ties with a paternal half-sister who causes harm, and what is the ruling on her marriage without the presence of her guardian, with the father's knowledge and consent after the marriage?

The Sharia commanded the upholding of kinship ties (Silat al-Rahim), but it did not specify a particular method or a defined extent for it. Rather, the reference for this is custom and varying circumstances. As for boycotting a sister because she has fallen into sins, the matter revolves around what serves the best interest (maslaha). Regarding her marriage without her father's permission: if the marriage contract was concluded without a guardian (wali), it is invalid according to the majority of scholars. If it was concluded with a more distant guardian, while her father was qualified for guardianship, and the father subsequently gave his consent, then there is a difference of opinion among scholars regarding the validity of her marriage. It is obligatory to re-conclude the marriage contract, especially if the sister was a virgin.