If you want to live in the UK after your marriage or civil partnership ceremony, you cannot come here as a visitor. Our Partners and families section explains how you can apply to come to the UK.
http://www.ukba.homeoffice.gov.uk/vi...g/marriage-cp/

its not possible for her to stay in the UK as she needs 'entry clearance' and you dont get that with a visitors for marriage visa.

and what visa will she use to gain entry to France ? Schengen or tourist visa ?

The applicant MUST be resident in the UK (excludes Scotland), e.g. Requires Leave To Remain in the UK as a work permit holder, HSMP etc..

http://www.visafrance.co.uk/spouseofEUnationals.php