I used to work on the mountain. A few years ago a poor girl was taken up the Watkin Path while pregnant by her idiot boyfriend and his equally moronic brothers. She had no clue what they were planning and was utterly unequipped for the conditions (was wearing flimsy trainers, the Watkin Path is challenging). We took her down by train (not an option at the moment, there is engineering work on the top section so all trains terminate at Clogwyn and Hafod Eryri is closed).
A family on the train took pity upon her and took her to wait in Pete's Eats while her boyfriend descended back to Nant Gwynant. She didn't even know where they'd come up from (I flicked through my photos on my phone until she recognised the scenery). When he did eventually turn up, the mother from the family gave him a bollocking to match the one the Summit Duty Manager had given. I don't think that it sank in how foolish he had been. I felt so sorry for her, I dread to think what sort of useless father he turned out to be.
So OP, if you are going to go up, then make sure that you are properly equipped for the conditions, both on the top and bottom. Appropriate footwear is essential too, in your case I'd recommend high-legged boots to mitigate against the risk of a twisted ankle - I wear hiking trainers when I fell run, but I accept that there is a risk in doing so.
Remember that there is:
- No access to the building at the Summit
- No trains from the Summit
- Nowhere to get drinking water once you've left Llanberis
- No food above Halfway House (if she's open)
- No shelter if the weather turns
- No space on trains (even from Clogwyn) if the winds are high/demand is low/demand is high/something's broken down...
Are you planning on doing everything in one day? How far are you travelling from? Llanberis is an hour from Bangor by bus, or 45 mins from Betws-y-Coed. The train service to Betws is sparse, only six per day. I've done the Llanberis Path in 1hr 10mins up, 1hr 30mins down, but equally I've seen people take four hours just to reach Clogwyn, never mind returning.