I will add my concurrence to the above. Especially continuing boys football, provided she has acceptance and support of her male teammates (presumably they are also her friends), their parents and her coach(es) – and as long as she is enjoying her football, and making technical progress. If you don’t think your own Boys team can provide that, for whatever reason, I would look at other local boys’ teams with coaches you respect. “Playing With The Boys”, by Niamh McKevitt (https://www.amazon.co.uk/Playing-Boys-Girl-Footballer-their-x/dp/1909534382
) is a relevant, and entertaining read in your context.
If she is a strong player in the Boys team, I wouldn’t necessarily suggest Girls Grassroots, unless she isn’t getting enough footy and provided she is then very disciplined about using it to develop her skills rather than to simply run amok (assuming she could). Besides practising her skills (youtube is a fantastic resource) at home or with friends, a complimentary alternative to fill the gaps would be to look at local athletics clubs to work on speed and stamina, which can only help her footy, especially in the summer off-season months. Humberside is well served for such clubs.
You could speak to an RTC about your own Boys team playing one of their teams in a friendly, or even asking local (Hull City?) Academy Boys if she could train with their Development squads if she is as good as their male recruits – it has been done before
It would be worth continuing to scout several RTCs over time, to keep assessing the standard, judge the atmosphere, pick the brains of the coaches, trial even, but only to join at a time/RTC where you and your daughter feel ready, and there is clear benefit in doing so – but do give it a go at some point, she can always revert to Boys football until u18s if she wants.
In terms of getting England recognition, I tend to agree with RosesAreRed’s comments about joining RTC at u14s, but it’s never too late to be spotted.
For example, an August 2016 RTC u16 signee (having only previously played Grassroots; Boys u7s to u15s, Girls u15 only), was scouted (presumably) and invited to a Regional Camp last November, National Camp in December, further Camps with International Friendlies in January, February and March 2017 before selection to England WU17s Team for the 2017 Euros. It might not always work like that, but it clearly can.
There is no “right” answer, as previous replies have said – the most important thing is that your daughter enjoys her football – after that, if she works hard and has a great attitude, the world is her oyster! Good luck to you and her!!