All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.
Divorcing through a text is a metaphor of divorce, which does not count unless the husband had the intention to issue a divorce by it, as has been underlined in fatwa 89894. If your husband intended to divorce his wife by writing this text, then divorce did take effect.
You should know that it is impermissible for you to ask for a divorce because your husband took a second wife. The Muslim wife is forbidden from asking for a divorce without a valid reason, as has previously been underlined in fatwa 131953. However, you bear no sin for the fact that your request for divorce caused your husband to divorce his second wife as long as you did not ask him to divorce her.
If your husband happened to take her back, then you should fear Allaah and be patient with any feeling of jealousy. Perhaps Allaah will make his marriage to her a source of good for all of you.
For more benefit, please refer to fataawa 81469 and 86818.
Allaah knows best.