The problem is, the divorce would be extremely difficult for her to get - I'd say impossible without Soames' co-operation. According to the 1857 act, proven adultery was sufficient cause, but the innocent party had to be the one suing for divorce.

The 1882 Married Women's property act granted women the right to their _own_ property, so Soames was not obligated to give her allowance, but he would have been obligated to give back the money (was it 50 pounds a year?) she had before marriage.

If Soames had divorced her she would have been a social pariah.
When John Galsworthy finally was able to marry Ada,(a divorced woman) he resigned from his club and all his trusteeships and such, because he wanted to pre-empt the possibility of being asked to leave.