Wales Coast Path - is it safe for a single female

This is the official safety advice

https://www.walescoastpath.gov.uk/plan-your-visit/wales-coast-path-safety-advice/?lang=en

If you mean will your daughter get attacked by strangers the chances of that happening anywhere in the UK is extremely small.

safety wise, what exactly are you concerned about?

On our trip in May, while walking on the path by St Davids, we came across a German young (mid-20s) lady walking different segments of the path, and she didn’t express any concerns.

There are certain safety standards about hiking alone no matter where you are hiking in the world.
1. Have a plan for where you will be hiking each day and communicate that plan to someone who will alert authorities if you don’t arrive at your destination.
2. Dress for changing weather or conditions.
3. Have adequate food and water if your hike should take longer than you expect.

I live near Olympic National Park and have seen the difference knowing which trail, or section of a trail, that a hiker was on has made to the effectiveness of search and rescue efforts.

Good advice so far. I trust you may have read (May, 2019) about the woman in Hawaii who repeated a simple trail she had been on before, without water, and was lost for several days, with considerable injury and large efforts by volunteer and paid searchers. I have reservations about "extreme sports" enthusiasts who endanger their (potential) rescuers, in the name of personal growth. But failure to consider what could go wrong with a non-extreme excursion is also irresponsible.

The Wales Coast path is obviously long and best advice would be to go on Google Maps and zoom down to look closely at the various sections. (Google have also done a ‘street view’ of some sections of the path). Can generally assumed to be safe although there are sections where you will only come across the occasional walker. Of course, when setting out, she could consider following a person or group who look ‘safe’. 2 weeks ago, I walked a section in Pembrokeshire and came across other walkers about every 13 minutes or so. Most were couples who looked like they had just retired. (This was not a school holiday week when things would have been different). Only came across 1 lone male in 45 minutes - buy hey, I was also a lone male. Some sections are quite busy whilst others have relatively few people.

Click the link and you will be taken to ’street view’ of part of the path in south Pembrokeshire. Click on the crosses to advance and go through the gate and down through the wood. You then go onto the sand to cross Barafundle Bay. Go up the steps on the other side and you will then find that the path is more busy as people walk from the nearest parking to the bay.
https://www.google.co.uk/maps/@51.6160132,-4.9016468,2a,75y,335.51h,92.76t/data=!3m6!1e1!3m4!1sw_39yBQ4PCF5l64Q-7URww!2e0!7i13312!8i6656!5m1!1e1

Here is another section of the path - near St.David’s in west Pembrokeshire >https://www.google.co.uk/maps/@51.8858275,-5.3051158,2a,60y,95.56h,83.07t/data=!3m6!1e1!3m4!1sGJATQ0eZCqWOHrdsTT-gfg!2e0!7i13312!8i6656!5m1!1e1

You might also like to consider going with some kind of group - although you would lose the freedom to do what you want. I recently came across www.explorebigblue.com who are based in Cardiff and run activities aimed at young people. This video gives you an idea of the kind of thing they do:>https://www.youtube.com/watch?v=qrEWdKSeurU

You didn't say if she was solo tent camping or going inn to inn.

An inn-to-inn alternative is to book a self-guided luggage supported walk. Example would be the Contours Walking Holiday tour agency that books accommodations, transports luggage and provides maps and directions. You could track progress and if your girl is a no-show you would at least be able to identify the walking stage that she went missing. And in all likelihood nothing bad will happen and she will have a memorable adventure.

https://www.contours.co.uk/pembrokeshire-coast-path

The disadvantage of single travel is UK rooms are typically more optimally priced per person for two to a room and singles pay a premium.

We encountered several solo walkers on one of English walking holidays. One woman was a fast and strong walker but really bad at route finding. She would usually walk with others but one day the group she was walking with branched off in a different direction to their nights accommodation. The solo walker got lost and ended up hitching a ride from a postal or milk driver to her B&B for the night. Her B&B host was so worried about her route finding ability she called other local B&Bs until she found ours and arranged to drop her off the next morning so she would have someone to walk with.

Carol, excellent advice to jenny-let someone know where you'll be and if possible, approximate timing. Many, many hikers have been rescued from our Colorado Rockies when hiking because they did that very thing. While I haven't done this trail myself, I think it is very popular and she won't be alone.

My Niece has traveled alone around the World...she has many Lifelong Friends. They often rendezvous again if they can and welcome each other into each others homes. If your daughter makes an effort to make friends along the way this will be her best memories from the trip. I, myself, used to travel alone before I was married. l was eating alone in the British Museum Café when a retired couple asked if they could join me. We had a lovely chat about the Roman Treasure exhibit and took each others addresses. We kept in touch and a couple years later they sent me a present for my Wedding. I was in Oxford at a local restaurant and found out about a Shakespeare Play open air in the Cloisters on Campus from two local ladies who invited me to accompany them, and lent me a lap blanket for the evening chill. So if she engages with other open friendly people she'll have a great time. Just don't put yourself in an awkward or uncomfortable situation.