Is it okay/healthy to continue giving distilled water to my 8 month with her feedings? We use arrowhead mountin spring water and they offer distilled water as well. Do babies meed flouride in their water?

Yes & yes. A water supplement is certainly ok for kids of any age. Distilled preparations do not have Fluoride & many bottled waters do not either.Fluoride would help baby form stronger enamel while they are building their teeth so it would be reasonable to make sure baby attained it in some form.Check with your doc about supplements if needed.
Yes, but precaution. Most infants should get enough fluid in their diet and formula. In warm weather, offering some extra water is fine, any approved brand is fine. Depending on local flouride levels, she may need fl drops but check w/ your md. But distilled water has no flouride. Be sure she is not taking water at times she should be getting formula.
No fluoride. Fluoride is useful applied directly to the teeth, then spit out. Multiple studies over the last 10-15 years have showed a lack of effectiveness and possible harm from ingesting fluoride. I recommend filtered water for babies.