gingo:
she’ll be going south,joining at , J11 and leaving at T2.
does she pay when she joins at J11. ? or when she leaves at T2 ?
or somewhere in between.
She will pay at the main toll between T4 and T3. It really isn’t difficult, a no brainer in fact. You get on the M6 Toll and drive until you have to stop because of a line of booths, with barriers, right across the carriageway.
Above each lane there will be a sign with a green arrow or a red cross, the ones with the arrows are open. Also on the sign, in one of the corners, there is a symbol that shows what is accepted at the booth and whether it is automatic or not. Bottom right will show a person and that means a manned booth, you can pay with cash or card here. Top left it shows a couple of credit cards, this means an unmanned booth that you use a card to pay at. All you do is slide your card into the slot, just as you would at an ATM, and a second or so later it spits your card back at you and the barrier lifts - off you go. If you want a receipt, you press the button marked Receipt before driving off. 
Top right it will show coins going into an opening, this is an unmanned booth and you pay with correct change only, throw it in the opening and once it has the correct amount the barrier lifts and off you go, exact amount only - no change given.
If there is a ‘T’ sign in the bottom left this lane can be also used by TAG users.
Some of the lanes will have more than one symbol, giving you different options to pay in that lane.
Her best bet, if she is concerned, is to us one of the lanes with the person symbol in the bottom right corner and just hand over her card or the cash, you can get change at these booths.
There really is nothing to it, no different to paying to enter or exit a car park.