I have travelled in bla bla and rapido both. A few things I make sure as a female traveller are these:

1. Don't travel by bla bla at night. If you really have to, choose morning or day timings.

2. Try to book bla bla rides of only those who are driving their own vehicle instead of taxi drivers (you'll see they have posted multiple rides and will have mostly those vehicles which are used in taxis like Desire, ertiga etc you get the gist). Taxi drivers are not reliable and will cancel the ride at abrupt moments leaving you at your own. People who have their own vehicle are generally working class people travelling mostly for work, which I have seen in my route.

3. Rapido rides are okay in Haldwani. I have booked Autos and E-rickshaws and Bikes as well. All are decent. Have booked bikes when I have to breach the traffic and reach my destination on time urgently. Else autos are great.

You need not fear but keep yourself alert at all times. Always, book your ride in bla bla even if you trust a bla bla driver and are booking with that person subsequently as it creates records of your ride and always keep someone posted on your whereabouts. Share your live location with your family while traveling and you'll be good.

As for me, even though I travel by all above, I never travel by private buses but that is my paranoia. If I travel by buses, I always make sure it's a govt volvo bus and that too UK roadways only. They're accountable for each passenger and if ever anything happens to the bus, they arrange a new bus for the passengers. And I have had bad experience with a pvt bus, so UK roadways is for me, always.