Is it ok to ask ex-dissertation supervisor for any future funded phds
The short answer is Yes. Rather, the supervisor might be happy to take you in if she had such a project.

Since you have already worked under the supervisor during your earlier degree and showed some excellent outcomes with research maturity, the supervisor would be really happy to take you in as a research lab member.

If you had not shown any good outcomes during your dissertation, then she might not consider the request.

However, it is not a waste of time to write and ask. Since she knows you she may read your email. Many a time, professors do not read emails even, and that is frustrating.