Can a heterosexual girl experience mild arousal from a female body? Given that the relationship was with guys.?

I think it's a pleasure for everyone to look at, so maybe.

Maybe. I am heterosexual: I always fell in love only with guys, and even simple sympathy arose only for guys. There was never even a hint of feelings for girls. However, I like to look at a beautiful female body, and yes, there was a mild arousal on multiple occasions. But not such that "I wish I could jump into bed with this girl", but purely abstract.

There is a theory that all people are bisexual. Some are more, some are less. If you trust her, then what you are experiencing is normal, and there is nothing unusual or terrible about it.

I have never experienced anything like this, so I dare to assume that heterosexual girls still cannot feel any attraction to the female body in principle.

Of course it can, but in this case, a "heterosexual" girl is likely to be bisexual, even though she had relationships with guys.