In fact it looks as though Mary Ann's previous husband had been a Joseph Thompson; the couple had their son James baptised at Wolsingham on 10 March 1850 (he shows as aged 11 in 1861).
Likely birth registrations:
Elizabeth Thompson mmn Wake, Dec qtr 1845 Weardale
Joseph Thompson mmn Wake, Sep qtr 1847 Weardale
James Thompson mmn Wake, Dec qtr 1849 Weardale
& Joseph Thompson marr Mary Ann Wake, Dec qtr 1844 Weardale.
Added:
Joseph is a maltster and grocer in 1851 (HO107/2388/387/28) so this looks very much like a dead end.